JP3735601B2 - Method for manufacturing compound semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a compound semiconductor device comprising a nitride-based compound semiconductor formed on a substrate.Manufacturing methodIn particular, compound semiconductor light emitting devicesManufacturing methodAbout.
[0002]
[Prior art]
At present, a nitride compound semiconductor having a general formula represented by BAlGaInN is known as a material for blue or violet light-emitting diodes. What is known as a light-emitting diode using this material is a MIS (Metal-Insulator-Semiconductor) structure. Such a MIS type light emitting diode has the disadvantages that the operating voltage is high, the light emission intensity is weak, and the lifetime of the element is short. As one of measures against these drawbacks, it is already known to use a pn junction type.
[0003]
The material system is grown on a sapphire substrate mainly by a metal organic chemical vapor deposition method (hereinafter referred to as MOCVD method) or a molecular beam epitaxy method (MBE method). Not limited to this method, nitride-based compound semiconductors have various problems.
[0004]
[Problems to be solved by the invention]
One of the problems of nitride-based compound semiconductors is a problem in the crystal growth process. Usually, in crystal growth using a non-equilibrium state such as MOCVD method or MBE method, crystal nuclei for growth are first formed, then the whole nuclei grow (three-dimensional growth), and then a plurality of nuclei combine to become flat. A film is formed, and finally the film grows in the growth axis direction (two-dimensional growth). When the present inventors performed crystal growth using sapphire as a substrate, especially in the growth of n-type crystals to which silicon was added, compared with a so-called undoped film or magnesium-doped p-type film that was not added intentionally. As a result, it has been found that it is difficult to obtain a flat film particularly in a thin film having a long transition time from three-dimensional growth to two-dimensional growth and having a thickness of 1 μm or less.
[0005]
The second is a problem relating to the essence of the crystal thus formed. It is well known that nitride compound semiconductors generally generate nitrogen vacancies in crystals because the vapor pressure of nitrogen is very high. This nitrogen vacancy forms a donor level with a deep energy level. Therefore, particularly in a light-emitting element, light generated in the light-emitting layer is absorbed by a low-energy transition related to the deep donor level, and the light extraction efficiency of the element is reduced. As a means for filling such nitrogen vacancies, it is known to use group V elements other than nitrogen, specifically phosphorus (P) or arsenic (As), as described in JP-A-49-29770. It has been. However, for example, when such an impurity is added to gallium nitride (GaN), gallium phosphide (GaP) or gallium arsenide (GaAs) has a significantly smaller energy gap than GaN. For this reason, in these mixed crystal semiconductors, the energy gap is remarkably lowered, and there is a problem that it is impossible to obtain light having a short wavelength utilizing the large energy gap that is a characteristic of nitride compound semiconductors.
[0006]
The third problem is the crystal quality. When nitride-based compound semiconductor films are formed on a semiconductor substrate such as Si or GaAs, which is usually used for forming semiconductor elements, the semiconductor substrates are grown on the substrate because they are cubic. In the nitride compound semiconductor film, the crystal form of the substrate is preserved, the epitaxial layer becomes a cubic film, and a hexagonal film cannot be obtained. For this reason, a hexagonal nitride compound semiconductor film has been obtained so far by using sapphire as a substrate. However, when this sapphire is used as a substrate, since the substrate is not conductive, it does not appear on the surface in a semiconductor element formed with a laminated nitride compound semiconductor film structure, particularly a normal light emitting element. It is necessary to etch away some layers from the surface when making electrical contact to the layers. As a result of experiments conducted by the present inventors, it has been found that a normal p-type nitride compound semiconductor crystal layer added with magnesium is very difficult to remove by etching treatment.
[0007]
The fourth is impurity diffusion, which is a problem related to the element formation process after crystal growth. In addition to the nitride-based compound semiconductor that is the subject of the present invention, in the manufacturing process of a semiconductor element, heat treatment is usually performed for various purposes after crystal growth. In this case, there is a problem that impurities desired to remain in a desired region due to heat treatment are diffused and adversely affect various characteristics of the device. As a result of experiments conducted by the present inventors, it has been found that diffusion of magnesium is the most significant among commonly used impurities.
[0008]
As described above, a nitride-based compound semiconductor film has difficulty in forming a flat thin film, the presence of nitrogen vacancies, difficulty in etching a crystal, heat treatment, from the viewpoint of the characteristics of the crystal itself or crystal growth. There are various problems such as diffusion of impurities in the process. These problems are particularly serious in forming a nitride-based compound semiconductor film semiconductor device using sapphire as a substrate, particularly a light-emitting device.
[0009]
The present invention has been made in view of the above problems,To provide a method for manufacturing a compound semiconductor device capable of improving the reliability and emission intensity of a semiconductor light emitting device.Objective.
[0010]
[Means for Solving the Problems]
First aspect of the present inventionIs an n-type or i-type formed by vapor phase growth, which is interposed between the crystal substrate, a semiconductor light emitting layer made of a nitride compound supported by the substrate, and the substrate and the semiconductor light emitting layer. A method of manufacturing a compound semiconductor device comprising: a first semiconductor layer made of a nitride-based compound, wherein the first semiconductor layer is formed as a flat thin film. ¹⁵ cm ^-3 ~ 1x10 ¹⁷ cm ^-3 Of magnesium or 1 × 10 ¹⁵ cm ^-3 ~ 1x10 ¹⁷ cm ^-3 It is characterized by adding zinc.
Second aspect of the present inventionIs an n-type or i-type formed by vapor phase growth, which is interposed between the crystal substrate, a semiconductor light emitting layer made of a nitride compound supported by the substrate, and the substrate and the semiconductor light emitting layer. A method of manufacturing a compound semiconductor device comprising: a first semiconductor region made of a nitride-based compound, wherein the first semiconductor region is formed with a 1 × 10 1 in order to form the first semiconductor region flat and thin. ¹⁵ cm ^-3 ~ 1x10 ¹⁷ cm ^-3 Of magnesium or 1 × 10 ¹⁵ cm ^-3 ~ 1x10 ¹⁷ cm ^-3 It is characterized by adding zinc.
The effect of the impurity element used in the embodiment according to the present invention to be described later is, The problem to be addressedByDifferent. Therefore, the effect of these elements on the problems will be described individually. The elements are divided into four groups: magnesium and zinc groups, carbon, oxygen, selenium and sulfur groups, silicon and hydrogen.
[0011]
First, the group of magnesium and zinc will be described. These elements are related to crystal flatness during growth, which is the first problem. As a result of experiments conducted by the inventors, as described above, the transition from three-dimensional growth to two-dimensional growth is slow in the n-type nitride compound semiconductor crystal film to which Si is added. For such growth, it was found that when magnesium was added at the same time, the transition from three-dimensional growth to two-dimensional growth occurred earlier than when no magnesium was added, that is, when the film thickness was thin. . That is, a flat thin film can be formed by adding magnesium. However, since magnesium is an acceptor impurity by nature, the addition of a large amount inhibits the formation of n-type crystals. Therefore, as a result of experiments conducted by the present inventors, the impurity concentration range in which the effect of addition can be obtained without inhibiting the formation of n-type crystals is 1 × 10 5 for magnesium.¹⁵cm^-3~ 1x10¹⁷cm^-3It turned out to be. A similar effect has been confirmed for zinc, and the concentration range where the effect appears is 1 × 10.¹⁵cm^-3~ 1x10¹⁷cm^-3It turned out to be.
[0012]
Next, the group of carbon, oxygen, selenium, and sulfur will be described. These elements relate to the problem of nitrogen vacancies in the crystal, which is the second problem. Since atoms of these elements easily enter nitrogen sites in nitride-based compound semiconductors, nitrogen vacancies unique to this compound semiconductor can be filled. Therefore, the deep donor level resulting from nitrogen vacancies can be eliminated. Further, since the above-described four kinds of impurity elements are impurities that form relatively shallow donors or acceptors, formation of a deep impurity level due to impurity addition does not occur. Therefore, nitrogen vacancies that form deep donor levels can be filled without causing loss of extraction efficiency. On the other hand, excessive addition of these impurities is undesirable because it leads to a decrease in luminous efficiency due to a decrease in crystallinity. For this reason, when an appropriate range of the impurity concentration is obtained, 1 × 10 10 is obtained for carbon.¹⁶cm^-3~ 5x10¹⁷cm^-31x10 for oxygen¹⁸cm^-3~ 1x10²⁰cm^-31x10 for selenium¹⁶cm^-3~ 1x10¹⁸cm^-3, Sulfur 1 × 10¹⁶cm^-3~ 1x10¹⁸cm^-3It turned out to be.
[0013]
Third, silicon will be described. This element relates to the third problem that is the difficulty of etching the crystal. As a result of experiments conducted by the present inventors, it was very difficult to remove by etching in a normal p-type nitride compound semiconductor crystal layer to which magnesium was added. However, it was found that etching can be easily performed when a small amount of silicon is added thereto. However, since silicon is an n-type donor impurity, excessive addition inhibits formation of p-type crystals. Therefore, as a result of experiments conducted by the inventors, the impurity concentration range in which the effect of addition can be obtained without inhibiting the formation of p-type crystals is 1 × 10.¹⁶cm^-3~ 8x10¹⁷cm^-3Was found to be silicon.
[0014]
Finally, hydrogen will be described. Consider a pn junction structure composed of an n-type GaN layer formed on a substrate and a p-type GaN layer to which magnesium (Mg) is added. When hydrogen is not contained in the n-type layer, when these structures are subjected to heat treatment, Mg diffuses from the p-type layer to the n-type layer. Such thermal diffusion is noticeable with respect to Mg among commonly used impurity elements. The thermal diffusion of Mg significantly reduces the carrier concentration of crystals that should be n-type and causes the n-type layer not to play the role of n-type. However, when an appropriate amount of hydrogen is contained in the n-type layer, Mg diffusion is suppressed, and Mg diffusion from the p-type layer to the n-type layer hardly occurs. Thus, hydrogen is considered to have an effect of suppressing the diffusion of impurities. As a result of experiments conducted by the present inventors, the range of hydrogen concentration capable of suppressing diffusion is 1 × 10.¹⁸cm^-3~ 1x10²⁰cm^-3It turned out to be.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0016]
(First embodiment)
FIG. 1 shows a cross section of a light emitting diode 10 according to a first embodiment of the present invention.
[0017]
The light emitting diode 10 has a sapphire substrate 11, and a buffer layer 12 having a thickness of 50 nm is formed on one main surface 11 a of the sapphire substrate 11 for the purpose of relaxing lattice mismatch. . Furthermore, on the buffer layer 12, an n-type GaN layer 13 having a thickness of 4 μm, an n-type InGaN light-emitting layer 14 having a thickness of 50 nm, a p-type AlGaN layer 15 having a thickness of 150 nm as a cladding layer, and a p-type having a thickness of 300 nm. A GaN layer 16 is stacked. The n-type GaN layer 13 also functions as a cladding layer.
[0018]
Each layer from the n-type GaN layer 13 to the p-type GaN layer 16 has 2 × 10¹⁷cm^-3Contains carbon. Further, as described in the second embodiment, a small amount of Si is added to the p-type AlGaN layer 15 and the p-type GaN layer 16 so that they can be easily etched.
[0019]
After crystal growth, the p-type GaN layer 16 to the n-type InGaN layer 14 are etched until the n-type GaN layer 13 is exposed, and then almost the entire surface is SiOnm having a thickness of 400 nm.₂Covered with a film 17. This SiO₂Holes are formed in necessary portions of the film 17, an Au—Ni film 18 is formed on the p-type layer 16, an Al film 19 is formed on the n-type layer 13, and an ohmic electrode is disposed.
[0020]
Below, the Example of the manufacturing method of the light emitting diode 10 is demonstrated in order.
[0021]
The light emitting diode 10 was manufactured by vapor phase growth by a well-known metal organic chemical vapor deposition method (MOCVD method). The gas used was ammonia (NH_Three), Silane (SiH)_Four) And carbon tetrachloride (CCl)_Four) And hydrogen (H₂) And nitrogen (N₂) Was used. Trimethylgallium ((CH_Three)_ThreeGa) (hereinafter referred to as TMG), trimethylaluminum ((CH_Three)_ThreeAl) (hereinafter referred to as TMA), trimethylindium ((CH_Three)_ThreeIn) (hereinafter referred to as TMI), dimethylzinc ((CH_Three)₂Zn) (hereinafter referred to as DMZ), biscyclopentadienylmagnesium ((C_FiveH_Five)₂Mg) (hereinafter Cp₂(Denoted as Mg).
[0022]
First, a single crystal sapphire substrate 11 having a c-plane 11a cleaned by organic cleaning, acid cleaning, and heat treatment as one main surface was mounted on a heatable susceptor mounted in a reaction chamber of an MOCVD apparatus. Next, H at normal pressure₂The main surface 11a of the sapphire substrate 11 was vapor-phase etched for about 10 minutes at a temperature of 1050 ° C. while flowing at a flow rate of 10 L / min.
[0023]
Next, the sapphire substrate 11 is cooled to 510 ° C., and H₂15L / min, N₂5L / min, NH_ThreeWas made to flow at a flow rate of 10 L / min and TMG at a flow rate of 25 cc / min for 6 minutes to form the buffer layer 12.
[0024]
Next, the sapphire substrate 11 is heated to 1020 ° C. and kept warm,₂15L / min, N₂5L / min, NH_Three10 L / min, TMG 25 cc / min, 100 ppm SiH_Four1 cc / min, and CCl_FourWas flown at a flow rate of 5 cc / min for 60 minutes to form an n-type GaN layer 13.
[0025]
Next, the sapphire substrate 11 is cooled to 800 ° C., and H₂5L / min, N₂15L / min, NH_Three10L / min, TMG 3cc / min, TMI 100cc / min, SiH_Four1 cc / min, DMZ 10 cc / min, and CCl_FourWas flown at a flow rate of 5 cc / min for 15 minutes to form an n-type InGaN layer 14.
[0026]
Next, the sapphire substrate 11 is heated to 1020 ° C. and kept warm,₂15L / min, N₂5L / min, NH_Three10L / min, TMG 50cc / min, TMA 25cc / min, Cp₂Mg 30cc / min, CCl_Four25 cc / min and SiH_FourWas flown at a flow rate of 0.1 cc / min for 5 minutes to form the p-type AlGaN layer 15.
[0027]
Furthermore, while keeping the sapphire substrate at 1020 ° C., H₂15L / min, N₂5L / min, NH_Three10L / min, TMG 25cc / min, Cp₂Mg 30cc / min, CCl_Four5 cc / min, and SiH_FourWas flown at a flow rate of 0.1 cc / min for about 5 minutes to form the p-type GaN layer 16. In this way, CCl_FourBy using as a growth gas, carbon can be contained in each growth layer.
[0028]
After this, TMG, Cp₂Mg and CCl_FourCut the flow of H₂15L / min, N₂5 L / min, and NH_ThreeThe sapphire substrate 11 was cooled to 700 ° C. while flowing at a flow rate of 10 L / min. In addition, H₂And NH_ThreeCut N₂The sapphire substrate 11 was left on the susceptor while holding at 5 L / min, and the temperature was lowered to room temperature (see FIG. 8).
[0029]
Where H₂And NH_ThreeCut N₂It is necessary that the temperature only be 300 ° C. or higher, and it is desirable that the temperature be 500 ° C. or higher. This is presumably because impurities near the surface of the grown crystal film are inactivated by active hydrogen in a high-temperature hydrogen atmosphere. Therefore, the percentage of impurities activated in such a high-temperature hydrogen atmosphere is only about 1%. In such a case, the non-activated impurity creates a lattice defect and becomes a non-radiative recombination center, so that the efficiency of the device is significantly reduced. On the other hand, when switching was performed at a high temperature as described above, it was found that at least 7% or more of the added impurities were activated in many cases.
[0030]
The substrate cooling rate is preferably 50 ° C./min or less. When cooling at a rate higher than this, especially in a mixed crystal system to which Al is added, for example, AlGaN, a thermal stress is applied to the crystal, so that a crack may occur on the crystal surface.
[0031]
Note that the gas used when the temperature is lowered to room temperature is N which is one of the constituent elements of the host crystal.₂However, it is also possible to use an inert gas such as He or Ar.
[0032]
By passing through such a process, it is no longer necessary to perform a process such as thermal annealing that has been conventionally used to improve the activation rate of impurities, so that the process can be simplified and the time required for manufacturing can be reduced. Shortening can also be achieved. Furthermore, a higher activation rate can be obtained than after a subsequent process such as thermal annealing.
[0033]
Next, the sapphire substrate 11 on which the nitride-based compound semiconductor layer is grown is taken out of the MOCVD apparatus, is used as a mask by using a resist or the like, and is etched with an alkaline aqueous solution until the n-type GaN layer 13 is exposed. did. Then, the surface is SiO₂A film 17 was formed to a thickness of about 400 nm. This film suppresses leakage current in the vicinity of the pn junction interface exposed on the side surface of the mesa structure and suppresses deterioration of the element.
[0034]
Next, SiO₂Holes were formed in the film 17 using a hydrofluoric acid-based solution so that the p-type GaN layer 16 was exposed with a size of about 100 μm square and the n-type GaN layer 13 was exposed with a size of about 100 μmφ. Through this hole, an Au—Ni film 18 of about 1 μm was formed on the p-type layer 16 and an Al film 19 of about 600 nm was formed on the n-type layer 13 to form an ohmic electrode. The light emitting diode was completed through the above steps.
[0035]
The impurity concentration of each layer in the light emitting diode 10 is 1 × 10 only for the Mg concentration in the p-type GaN layer 16.²⁰cm^-3The concentrations of Si, Zn, and Mg contained in the n-type GaN layer 13, the n-type InGaN layer 14, and the p-type AlGaN layer 15 are 2 × 10, respectively.¹⁹cm^-3Met. The carbon concentration contained in each layer from the n-type GaN layer 13 to the p-type GaN layer 16 is 2 × 10.¹⁷cm^-3Met.
[0036]
The light emitting diode 10 thus formed was diced to a size of about 350 μm square, mounted on a stem, molded, and formed into a lamp. In the light emitting diode thus formed, a light output of about 2 to 3 mW was obtained with respect to a forward current of 20 mA, and a lifetime of about 20,000 hours could be realized. These values are improved by about 2-3 times compared to the characteristics of light-emitting diodes having a similar structure in which carbon is substantially not included, that is, below the detection limit at the time of measurement. Yes.
[0037]
This carbon concentration is 1 × 10¹⁶cm^-3To 5 × 10¹⁷cm^-3The effects described above have been seen in the previous areas. When the amount was less than this, the extraction efficiency decreased due to the formation of deep levels by nitrogen vacancies. That is, the effect of carbon addition did not appear. On the other hand, when the amount is larger than this range, carbon precipitates in the crystal, causing non-radiative recombination centers and crystal defects, and the effect is not exhibited. In order for the effect to appear remarkably, the carbon concentration is 5 × 10¹⁶cm^-3And 5 × 10¹⁷cm^-3It is desirable that the carbon concentration is 1 × 10¹⁷cm^-3To 3 × 10¹⁷cm^-3When it was in the range up to, the extraction efficiency took a maximum value.
[0038]
Although the case where the light emitting layer is made of InGaN has been described here, the same effect can be obtained even when the light emitting layer is made of GaN or InGaAlN.
[0039]
(Second Embodiment)
FIG. 2 shows a cross section of a light emitting diode 20 according to a second embodiment of the present invention.
[0040]
The light emitting diode 20 has a sapphire substrate 21, and a GaN buffer layer 22 is formed on the sapphire substrate 21 with a thickness of 50 nm in order to alleviate lattice mismatch. On the buffer layer 22, an n-type GaN layer 23 having a thickness of 3 μm, an n-type InGaN light emitting layer 24 having a thickness of 100 nm, a p-type AlGaN layer 25 having a thickness of 300 nm as a cladding layer, and a p-type having a thickness of 500 nm. A GaN layer 26 is stacked.
[0041]
The impurity concentration of each layer is as follows. In the p-type GaN layer 26, the Mg concentration is 1 × 10.²⁰cm^-3, Si concentration is 1 × 10¹⁷cm^-3It is. In the p-type AlGaN layer 25, the Mg concentration is 2 × 10.¹⁹cm^-3, Si concentration is 1 × 10¹⁷cm^-3It is. In the n-type InGaN layer 24, the Si concentration is 2 × 10.¹⁹cm^-3Zn concentration is 1 × 10¹⁸cm^-3It is. The Si concentration in the n-type GaN layer 23 is 2 × 10.¹⁹cm^-3It is.
[0042]
Below, the Example of the manufacturing method of the light emitting diode 20 is described in order.
[0043]
First, a single crystal sapphire substrate 21 having a main surface (a (11-20) plane) cleaned by organic cleaning, acid cleaning and heat treatment is placed on a heatable susceptor placed in a reaction chamber of an MOCVD apparatus. Installed. Next, H at normal pressure₂The main surface of the sapphire substrate 21 was vapor-phase etched at a temperature of 1050 ° C. for about 10 minutes while flowing at a flow rate of 10 L / min.
[0044]
Next, the sapphire substrate 21 is cooled to 510 ° C., and H₂15L / min, N₂10L / min, NH_ThreeWas made to flow at a flow rate of 5 L / min and TMG at a flow rate of 25 cc / min to form the buffer layer 22.
[0045]
Next, the sapphire substrate 21 is heated to 1020 ° C. and kept warm, and H₂15L / min, N₂10L / min, NH_Three5L / min, TMG 25cc / min, SiH_FourWas flown at a flow rate of 5 cc / min for 60 minutes to form an n-type GaN layer 23.
[0046]
Next, the sapphire substrate 21 is cooled to 800 ° C., and H₂10 L / min, N₂15L / min, NH_Three5 L / min, triethylgallium ((C₂H_Five)_ThreeGa) (hereinafter referred to as TEG) 3 cc / min, TMI 30 cc / min, DMZ 1 cc / min, SiH_FourWas flown at a flow rate of 1 cc / min for 30 minutes to form an n-type InGaN layer 24. Zn addition in this layer formation has the role of assisting flat thin film growth as well as the role of light emission center.
[0047]
Next, the sapphire substrate 21 is heated to 1020 ° C. and kept warm, and H₂15L / min, N₂10L / min, NH_Three5L / min, TMG 50cc / min, TMA 25cc / min, Cp₂Mg 50cc / min, SiH_FourWas flown at a flow rate of 1 cc / min for 10 minutes to form a p-type AlGaN layer 25.
[0048]
Furthermore, the sapphire substrate 21 is kept at 1020 ° C., and H₂15L / min, N₂10L / min, NH_Three5L / min, TMG 25cc / min, Cp₂Mg 100cc / min, SiH_FourWas flown at a flow rate of 1 cc / min for about 10 minutes to form the p-type GaN layer 26.
[0049]
After this, TMG, Cp₂Mg and SiH_FourCut H₂15L / min, N₂10L / min, NH_ThreeThe sapphire substrate 21 was cooled to 800 ° C. while flowing at a flow rate of 5 L / min. Then N₂The sapphire substrate 21 was left on the susceptor while flowing 10 L / min, and the temperature was lowered to room temperature.
[0050]
Next, the sapphire substrate 21 on which the nitride-based compound semiconductor layer is grown is taken out of the MOCVD apparatus, and is used as a mask by using a resist or the like, and is etched with an alkaline aqueous solution until the n-type GaN layer 23 is exposed. did. Then, the surface is SiO₂A film 27 was formed to a thickness of about 200 nm. This film suppresses leakage current in the vicinity of the pn junction interface exposed on the side surface of the mesa structure and suppresses deterioration of the element.
[0051]
Next, SiO₂Holes were formed in the film 27 using a hydrofluoric acid-based solution so that the p-type GaN layer 26 was exposed with a size of about 100 μm square and the n-type GaN layer 23 was exposed with a size of about 120 μmφ. Through this hole, an Au—Ni film 28 of about 2 μm was formed on the p-type GaN layer 26 and an Al—Ti film 29 of about 1 μm was formed on the n-type layer 23 to form an ohmic electrode.
[0052]
The light-emitting diode 20 thus formed was diced to a size of about 350 μm square, mounted on a stem, molded, and formed into a lamp. The light emitting diode 20 formed in this way showed the same performance as the light emitting diode 10 shown in the first embodiment in light emission intensity and reliability.
[0053]
In the light emitting diode 20, the Si concentration in the p-type GaN layer 26 and the p-type AlGaN layer 25, which is the gist of the present invention, is 2 × 10 2 as described above.¹⁷cm^-3Met. At this concentration, the p-type GaN layer 26 and the p-type AlGaN layer 25 can be removed by etching, and an element can be formed. The concentration at which etching was possible was 1 × 10¹⁶cm^-3Needed more. On the other hand, since Si is essentially a donor impurity, excessive addition causes a problem that the GaN layer 26 and the AlGaN layer 25 that should be p-type are changed to n-type. Therefore, although the upper limit of the Si concentration depends on the acceptor concentration of the layer, the p-type carrier concentration necessary for element formation is 1 × 10.¹⁸cm^-3Therefore, the Si concentration is 8 × 10¹⁷cm^-3In the following, it was found that there is little change to n-type. Furthermore, the Si concentration is 5 × 10¹⁷cm^-3Desirably, the following is desirable: 5 × 10¹⁶cm^-35 × 10 or more¹⁷cm^-3The following concentrations were the most desirable for device formation.
[0054]
(Third embodiment)
FIG. 3 shows a cross section of a light emitting diode 30 according to a third embodiment of the present invention.
[0055]
The light-emitting diode 30 includes a crystalline AlN substrate 31. On the AlN substrate 31, an n-type AlGaN layer 33 having a thickness of 4 μm, an n-type GaN light-emitting layer 34 having a thickness of 100 nm, and a cladding layer are sequentially formed. A p-type AlGaN layer 35 having a thickness of 300 nm and a p-type GaN layer 36 having a thickness of 500 nm are stacked. Also, oxygen is 1 × 10 6 in each layer from the n-type AlN layer 33 to the p-type GaN layer 36.¹⁸cm^-3Contained.
[0056]
Below, the Example of the manufacturing method of the light emitting diode 30 is described in order.
[0057]
First, the AlN substrate 31 cleaned by organic cleaning, acid cleaning and heat treatment was mounted on a heatable susceptor placed in the reaction chamber of the MOCVD apparatus. Next, H at normal pressure₂The main surface of the AlN substrate was vapor-phase etched at a temperature of 1050 ° C. for about 10 minutes while flowing 10 L / min.
[0058]
Next, the temperature of the AlN substrate 31 is lowered to 1000 ° C.₂15L / min, N₂10L / min, NH_Three5L / min, TMA 25cc / min, TMG 50cc / min, SiH_Four1 cc / min, 0.1% diluted oxygen (O₂) At a flow rate of 20 cc / min for 60 minutes to form an n-type AlGaN layer 33.
[0059]
Next, while maintaining the AlN substrate 31 at 1000 ° C., H₂10 L / min, N₂15L / min, NH_Three5L / min, TEG 3cc / min, DMZ 10cc / min, SiH_Four1 cc / min diluted oxygen O₂Was flown at a flow rate of 300 cc / min for 4 minutes to form an n-type GaN layer 34.
[0060]
Next, the AlN substrate is kept at 1000 ° C. and H₂15L / min, N₂10L / min, NH_Three5L / min, TMG 50cc / min, TMA 25cc / min, Cp₂O diluted with 100 cc / min Mg₂Was flown at a flow rate of 200 cc / min for 5 minutes to form a p-type AlGaN layer 35.
[0061]
Further, while keeping the AlN substrate at 1000 ° C., H₂15L / min, N₂10L / min, NH_Three5L / min, TMG 50cc / min, Cp₂O diluted with 30 cc / min Mg₂Was flown at a flow rate of 200 cc / min for about 20 minutes to form the p-type GaN layer 36.
[0062]
Thereafter, the temperature of the AlN substrate 31 is lowered to 900 ° C., and NH_Three10 L / min, N₂Was left on the susceptor while flowing at a flow rate of 10 L / min.
[0063]
The AlN substrate 31 on which the nitride-based compound semiconductor layer was grown was taken out of the MOCVD apparatus, used as a mask by using a resist or the like, and etched with an alkaline aqueous solution until the n-type AlGaN layer 33 was exposed to form a mesa structure. Then, the surface is SiO₂A film 37 was formed with a thickness of about 300 nm. This film suppresses leakage current in the vicinity of the pn junction interface exposed on the side surface of the mesa structure and suppresses deterioration of the element.
[0064]
Next, SiO₂Holes were formed in the film 37 using a hydrofluoric acid-based solution so that the p-type GaN layer 36 was exposed to a size of about 100 μm square and the n-type AlGaN layer 33 was exposed to a size of about 100 μmφ. Through this hole, an Au—Ni film 38 of about 2 μm was formed on the p-type GaN layer 36 and an Al film 39 of about 1 μm was formed on the n-type AlGaN layer 33 to form an ohmic electrode.
[0065]
The light emitting diode 30 thus formed was diced to a size of about 400 μm square, mounted on a stem, molded, and formed into a lamp. The light-emitting diode 30 formed in this way showed the same performance as the light-emitting diode 10 shown in the first embodiment in light emission intensity and reliability.
[0066]
In the light emitting diode 30, the impurity concentration of each layer is 1 × 10 only for the Mg concentration in the p-type GaN layer 36.²⁰cm^-3The concentrations of Si, Zn, and Mg contained in the n-type AlGaN layer 33 to the p-type AlGaN layer 35 are 2 × 10¹⁹cm^-3Met. Further, the oxygen concentration which is a feature of the present embodiment is the above-mentioned value 1 × 10.¹⁸cm^-31x10 including¹⁸cm^-3To 1 × 10²⁰cm^-3The effect of filling nitrogen vacancies in the region up to was observed. When the amount was less than this, no effect was observed in the emission intensity. On the other hand, if it is larger than this range, there is a risk of explosion in the apparatus, which causes a problem in the safety of the apparatus. 1 × 10 among these¹⁸cm^-3To 1 × 10¹⁹cm^-3The characteristics of the light-emitting element were most improved when the oxygen concentration was.
[0067]
(Fourth embodiment)
FIG. 4 shows a cross section of a light emitting diode 40 according to a fourth embodiment of the present invention.
[0068]
The light emitting diode 40 has a sapphire substrate 11, and a buffer layer 42 is formed on one main surface of the sapphire substrate 11 with a thickness of 50 nm in order to reduce lattice mismatch. On the buffer layer 42, an n-type GaN layer 43 having a thickness of 4 μm, an n-type InGaN light emitting layer 44 having a thickness of 50 nm, a p-type AlGaN layer 45 having a thickness of 150 nm as a cladding layer, and a p-type having a thickness of 300 nm. A GaN layer 46 is stacked. These n-type GaN layer 43 and n-type InGaN layer 45 each have 5 × 10 hydrogen.¹⁸cm^-3include.
[0069]
Further, after crystal growth, the n-type InGaN layer 44 to the p-type GaN layer 46 are etched until the n-type GaN layer 43 is exposed, and then almost the entire surface is SiOnm having a thickness of 400 nm.₂Covered with a film 47. This SiO₂A hole is formed in a necessary portion of the film 47, an Au—Ni film 48 is formed on the p-type layer 46, an Al film 49 is formed on the n-type layer 43, and an ohmic electrode is provided.
[0070]
Below, the Example of the manufacturing method of the light emitting diode 40 is demonstrated in order.
[0071]
First, a single crystal sapphire substrate 11 having a C surface as a main surface cleaned by organic cleaning, acid cleaning, and heat treatment was mounted on a heatable susceptor placed in a reaction chamber of an MOCVD apparatus. Next, H at normal pressure₂The sapphire substrate 11 was vapor-phase etched at a temperature of 1100 ° C. for about 10 minutes while flowing at a flow rate of 20 L / min.
[0072]
Next, the sapphire substrate 11 is cooled to 500 ° C., and H₂15L / min, N₂10L / min, NH_ThreeWas flown at a flow rate of 5 L / min, TMG at 25 cc / min, and TMA at 40 cc / min to form the buffer layer 42.
[0073]
Next, the sapphire substrate 11 is heated to 1020 ° C. and kept warm,₂20L / min, N₂10L / min, NH_Three10L / min, TMG 25cc / min, SiH_FourWas flown at a flow rate of 1 cc / min for 60 minutes to form an n-type GaN layer 43.
[0074]
Next, the sapphire substrate 11 is cooled to 800 ° C., and H₂20L / min, N₂15L / min, NH_Three10 L / min, TEG 3 cc / min, TMI 30 cc / min, DMZ 1 cc / min, SiH_FourWas flown at a flow rate of 1 cc / min for 15 minutes to form an n-type InGaN layer 44.
[0075]
Next, the temperature of the sapphire substrate 11 is increased to 1020 ° C. and kept warm,₂15L / min, N₂10L / min, NH_Three10L / min, TMG 50cc / min, TMA 25cc / min, Cp₂Mg 30cc / min, SiH_FourWas flown at a flow rate of 0.1 cc / min for 5 minutes to form a p-type AlGaN layer 45.
[0076]
Further, while keeping the sapphire substrate 11 at 1020 ° C., H₂15L / min, N₂10L / min, NH_Three10L / min, TMG 50cc / min, Cp₂Mg 100cc / min, SiH_FourWas flown at a flow rate of 0.1 cc / min for about 5 minutes to form the p-type GaN layer 46. In the growth of the p-type AlGaN layer 45 and the p-type GaN layer 46, Si was added for the ease of etching described in the second embodiment.
[0077]
Thereafter, the sapphire substrate 11 is cooled to 800 ° C. and N₂Was left on the susceptor while flowing at 10 L / min.
[0078]
The sapphire substrate 11 on which the nitride-based compound semiconductor layer is grown is taken out of the MOCVD apparatus, and the surface is SiO 2 by the CVD apparatus.₂A film 47 was formed with a thickness of about 400 nm. This SiO₂Using the film 47 as a mask, etching was performed by a known reactive ion etching method (RIE method) until the n-type GaN layer 43 was exposed to form a mesa structure. This SiO₂Holes were formed in the film 47 using a hydrofluoric acid-based solution so that the p-type GaN layer 46 was exposed with a size of about 100 μm square. Through this hole, an Au—Ni film 48 of about 1 μm was formed on the p-type layer 46, and an Al film 49 of about 600 nm was formed on the n-type layer 43 to form ohmic electrodes.
[0079]
The light emitting diode 40 formed in this way was diced to a size of about 350 μm square and then made into a lamp. The light emitting diode 40 formed in this way had the same light emission intensity and reliability as the light emitting diode 10 described above.
[0080]
The impurity concentration of each layer in the light emitting diode 40 is 1 × 10 only for the Mg concentration in the p-type GaN layer 46.²⁰cm^-3The concentrations of Si, Zn, and Mg contained in the n-type GaN layer 43 to the p-type AlGaN layer 45 are 2 × 10¹⁹cm^-3Met. The hydrogen concentration contained in the n-type GaN layer 43 and the n-type InGaN layer 44, which is the gist of the present invention, is 5 × 10.¹⁸cm^-3But 3 × 10¹⁸cm^-3To 1 × 10²⁰cm^-3In the region up to this point, Mg diffusion from the p-type AlGaN layer 45 and the p-type GaN layer 46 could be suppressed. When the amount is smaller than this, the diffusion of Mg into the n-type layers 43 and 44 is remarkable, and a phenomenon that these layers become insulating layers due to a compensation effect or change into p-type is observed. On the other hand, when there is more hydrogen than this, hydrogen couple | bonded with the impurity element which becomes a factor of a carrier, and it became a factor of carrier inactivation. Therefore, the hydrogen concentration is in the above range 3 × 10¹⁸cm^-3To 1 × 10²⁰cm^-3Need to be. More desirably, 3 × 10¹⁸cm^-3To 1 × 10¹⁹cm^-3The effect was noticeable when the concentration was about a certain level.
[0081]
(Fifth embodiment)
FIG. 5 shows a cross section of a light emitting diode 50 according to a fifth embodiment of the present invention.
[0082]
The fifth embodiment is greatly different from the above-described four embodiments in that SiC is used for the substrate. The main impurities in each nitride semiconductor layer are N (nitrogen) for the SiC substrate 51, Si for the n-type GaN layer 53, Si and Zn for the n-type InGaN light-emitting layer 54, and p-type AlGaN layer 55 and p-type which are cladding layers. The GaN layer 56 is Mg. Regarding these concentrations, as in the above-described four embodiments, Zn in the n-type InGaN layer 54 and Mg in the p-type AlGaN layer 55 are 2 × 10.¹⁹cm^-31 × 10 for Mg in the p-type GaN layer 56²⁰cm^-3It is. For Si, the n-type layers 53 and 54 are 1 × 10 5.¹⁹cm^-3About 8 × 10 with p-type layers 55 and 56¹⁶cm^-3It is. As other impurities, each layer from the n-type GaN layer 53 to the p-type GaN layer 56 contains 1 × 10 carbon.¹⁸cm^-3, Oxygen is 1 × 10¹⁸cm^-3include.
[0083]
As for the manufacturing method, the MOCVD method was used as in the four embodiments described so far. In this embodiment, in addition to the same effects as those of the first and second embodiments, the crystal defect density is also greatly reduced, and the light emission intensity is about twice as long as that of the light-emitting diode 10, and the lifetime is increased. It was possible to improve the performance about three times.
[0084]
(Sixth embodiment)
FIG. 6 shows a cross section of a laser diode 60 according to a sixth embodiment of the present invention.
[0085]
The laser diode 60 has a sapphire substrate 61. On the sapphire substrate 61, a GaN buffer layer 62 having a thickness of 50 nm, an n-type GaN layer 63 having a thickness of 2 μm, and an n-type AlGaN having a thickness of 500 nm (Al Composition ratio 0.3) layer 64, 100 nm thick undoped GaN layer 65, 500 nm thick p-type AlGaN (Al composition ratio 0.3) layer 66, and 300 nm thick p-type GaN layer 67. ing.
[0086]
The impurity concentration of each of these layers is such that Si in the n-type GaN layer 63 is 2 × 10.¹⁹cm^-3And Mg is 5 × 10¹⁶cm^-3In the n-type AlGaN layer 64, Si is 2 × 10.¹⁹cm^-3And Mg is 8 × 10¹⁶cm^-3In the undoped GaN layer 65, Mg is 1 × 10¹⁷cm^-3In the p-type AlGaN layer 66, Mg is 3 × 10.¹⁹cm^-3In the p-type GaN layer 67, Mg is 1 × 10²⁰cm^-3It is.
[0087]
The manufacturing method of this element was carried out in the same manner as the embodiments shown so far. In each layer from the n-type GaN layer 63 to the undoped GaN layer 65, Mg was added at the above-mentioned concentration for forming a flat thin film. The concentration of Mg is 1 × 10¹⁵cm^-3~ 1x10¹⁷cm^-3The effect was seen. When the amount was less than this, a flat thin film could not be obtained. On the other hand, when the amount is larger than this, the n-type layer has a reduced carrier concentration, and Si must be added, making it difficult to obtain a flat film. Therefore, the Mg concentration is 1 × 10¹⁵cm^-3~ 1x10¹⁷cm^-3Is suitable, 1 × 10¹⁶cm^-3~ 1x10¹⁷cm^-3It is desirable that the concentration be
[0088]
(Seventh embodiment)
FIG. 7 shows a cross section of a light emitting diode 70 according to a seventh embodiment of the present invention.
[0089]
The light emitting diode 70 is formed on a sapphire substrate 71 having an a-plane ((11-20) plane) as a main surface. The layer structure is, in order from the sapphire substrate 71, a GaN buffer layer 72, a Zn-doped GaN layer 73, a Si-doped n-type GaN layer 74, an n-type InGaN light-emitting layer 75, a Mg-doped p-type AlGaN layer 76, and a Mg-doped p-type GaN layer 77. It is.
[0090]
The GaN buffer layer 72 has a thickness of 0.1 μm, so as to alleviate the lattice mismatch between the sapphire substrate and the GaN layer. The GaN layer 73 has a thickness of 0.3 μm, and Zn is added to promote the two-dimensional growth that is the gist of the present invention. The concentration of Zn is 1 × 10¹⁵cm^-3~ 1x10¹⁷cm^-3Is suitable, 1 × 10¹⁵cm^-3~ 3x10¹⁶cm^-3It is desirable that the concentration be The Si-doped n-type GaN layer 74 has a thickness of 4 μm and is for injecting electrons into the light emitting layer. In addition, since sapphire that is an insulator is used for the substrate, the n-type layer must be exposed by etching, so the layer 74 is formed thicker. The carrier concentration of the layer 74 is 2 × 10¹⁸cm^-3Degree.
[0091]
The n-type InGaN light emitting layer 75 has a thickness of 0.3 μm. Further, in order to adjust the emission wavelength to about 450 nm, Si and Zn are simultaneously added when the In composition ratio is 6%. When the In composition is increased to about 30%, the emission wavelength can be adjusted by adding only Si.
[0092]
The Mg-doped p-type AlGaN layer 76 has a thickness of 0.2 μm and functions to inject holes into the light emitting layer. Further, the Al composition ratio is desirably large in order to suppress the overflow of electrons, whereas the composition ratio is desirably small in order to ensure the p-type carrier concentration. Due to the combination of these conditions, the Al composition ratio is desirably in the range of 5% to 25%, and more desirably in the range of 10% to 20%.
[0093]
The Mg-doped p-type GaN layer 77 has a thickness of 0.2 μm, and the AlGaN layer 76 is formed because it is difficult to make a good ohmic contact. Carrier concentration is 1 × 10¹⁸cm^-3It is desirable that there be about 2 or more in this case.¹⁸cm^-3Was set. A small amount of Si was added to the p-type layers 76 and 77 in consideration of the realization of etching.
[0094]
As the ohmic electrode, a stacked structure 78 of Ni 20 nm and Au 300 nm was formed on both layers of pn, and after heat treatment for forming a good ohmic electrode, a stacked structure 79 of Ti 50 nm and Au 2 μm was further formed for bonding. . Such a light emitting diode 70 has a luminance of about 2 cd at 20 mA.
[0095]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. Although the light-emitting element has been described in the above embodiment, a thin film transistor using the film described in the above embodiment for a channel region, a heterojunction bipolar transistor using an emitter, a base, and a collector can be realized. In this case, since a transistor can be formed using a film with improved crystallinity, a device capable of high-speed operation can be expected.
[0096]
【The invention's effect】
According to the method for manufacturing a compound semiconductor device according to the present invention, the reliability and emission intensity of the semiconductor light emitting device can be improved.
[Brief description of the drawings]
FIG. 1 is a structural cross-sectional view of a light-emitting element according to a first embodiment of the present invention.
FIG. 2 is a structural cross-sectional view of a light emitting device according to a second embodiment of the present invention.
FIG. 3 is a structural cross-sectional view of a light emitting device according to a third embodiment of the present invention.
FIG. 4 is a structural cross-sectional view of a light emitting device according to a fourth embodiment of the present invention.
FIG. 5 is a structural cross-sectional view of a light emitting device according to a fifth embodiment of the present invention.
FIG. 6 is a structural cross-sectional view of a light emitting device according to a sixth embodiment of the present invention.
FIG. 7 is a structural cross-sectional view of a light emitting device according to a seventh embodiment of the present invention.
FIG. 8 is a view for explaining an operation when the temperature is lowered in the method for manufacturing the light emitting element according to the first embodiment of the invention.
[Explanation of symbols]
11, 21, 61, 71 ... sapphire substrate, 31 ... AlN substrate, 51 ... SiC substrate, 12, 22, 42, 62, 72 ... buffer layer, 13, 23, 43, 53, 63, 74 ... n-type GaN layer 33, AlGaN layer, 14, 24, 44, 54, 75 ... n-type InGaN light emitting layer, 34 ... GaN light emitting layer, 15, 25, 35, 45, 55, 66, 76 ... p-type AlGaN layer, 16, 26 36, 46, 56, 67, 77 ... p-type GaN layer, 64 ... n-type AlGaN layer, 65 ... undoped GaN layer, 73 ... Zn-doped GaN layer.

Claims (12)

A crystal substrate, a semiconductor light-emitting layer made of a nitride compound formed on the crystal substrate, and an n-type or i-type formed by vapor phase growth interposed between the crystal substrate and the semiconductor light-emitting layer a manufacturing method of a first semiconductor layer made of a nitride-based compound comprises a compound semiconductor device, magnesium ^{1 × 10 15 cm -3 ~1 ×} 10 17 cm -3 in the first semiconductor layer or method of manufacturing a compound semiconductor device, characterized in that the addition of zinc ^{1 × 10 15 cm -3 ~1 ×} 10 17 cm -3. The semiconductor device further includes a second semiconductor layer stacked on the semiconductor light emitting layer on the opposite side of the first semiconductor layer, and the second semiconductor layer is made of a nitride-based compound containing magnesium, 2. The compound semiconductor device according to claim 1, wherein in the manufacturing method, hydrogen of 3 × 10 ¹⁸ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ is added to the first semiconductor layer or the semiconductor light emitting layer. Manufacturing method. The semiconductor light-emitting layer and at least hand in the ^{1 × 10 16 cm -3 ~5 ×} 10 17 cm -3 carbon of the semiconductor layer, the ^{1 × 10 18 cm -3 ~1 ×} 10 20 cm -3 oxygen, 1 × 10 ¹⁶ cm ^-3 to 1 × of 10 ¹⁸ cm ^-3 selenium, or ^{1 × 10 16 cm -3 ~1 ×} 10 18 claim 1 or 2, characterized in that the addition of sulfur cm ^-3 The manufacturing method of the compound semiconductor device. 4. The method of manufacturing a compound semiconductor device according to claim 1, wherein the first semiconductor layer is made of an n-type nitride compound. The semiconductor device are that comprises a semiconductor lamination portion made of nitride-based compound constituting the light emission element on the crystal substrate, the light-emitting layer and the semiconductor layer included in the semiconductor lamination portion, the semiconductor lamination 5. The method of manufacturing a compound semiconductor device according to claim 4, wherein each layer included in the portion is made of a material selected from the group consisting of GaN, InGaN, AlGaN, and InGaAlN. 6. The method of manufacturing a compound semiconductor device according to claim 1, wherein a buffer layer made of a nitride compound is formed between the crystal substrate and the first semiconductor layer. A crystal substrate, a semiconductor light-emitting layer made of a nitride compound formed on the crystal substrate, and an n-type or i-type formed by vapor phase growth interposed between the crystal substrate and the semiconductor light-emitting layer a manufacturing method of a first semiconductor region made of a nitride-based compound comprises a compound semiconductor device, magnesium ^{1 × 10 15 cm -3 ~1 ×} 10 17 cm -3 in the first semiconductor region or method of manufacturing a compound semiconductor device, characterized in that the addition of zinc ^{1 × 10 15 cm -3 ~1 ×} 10 17 cm -3. The semiconductor device further includes a second semiconductor region stacked on the semiconductor light emitting layer on the opposite side of the first semiconductor region, and the second semiconductor region is made of a nitride-based compound containing magnesium, 8. The compound semiconductor device according to claim 7, wherein in the manufacturing method, hydrogen of 3 × 10 ¹⁸ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ is added to the first semiconductor region or the semiconductor light emitting layer. Manufacturing method. The semiconductor light-emitting layer and at least hand in the ^{1 × 10 16 cm -3 ~5 ×} 10 17 cm -3 carbon of the semiconductor region, the ^{1 × 10 18 cm -3 ~1 ×} 10 20 cm -3 oxygen, 1 × 10 ¹⁶ cm selenium ^{-3 ~1} × 10 ¹⁸ cm ^-3, or according to ^{1 × 10 16 cm -3 ~1 ×} 10 18 cm claim 7 or 8, characterized in that the addition of sulfur ^-3 The manufacturing method of the compound semiconductor device. The method of manufacturing a compound semiconductor device according to claim 7, wherein the first semiconductor region is made of an n-type nitride-based compound. The semiconductor device are that comprises a semiconductor lamination portion made of nitride-based compound constituting the light emission element on the crystal substrate, the semiconductor light-emitting layer and the semiconductor region contained in the semiconductor lamination portion, the semiconductor The method for manufacturing a compound semiconductor device according to claim 10, wherein each layer included in the stacked portion is made of a material selected from the group consisting of GaN, InGaN, AlGaN, and InGaAlN. The method of manufacturing a compound semiconductor device according to claim 7, wherein a buffer layer made of a nitride compound is formed between the crystal substrate and the first semiconductor region.

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