JP4149054B2 - Semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device using a III-V group nitride compound semiconductor. Here, the group III-V nitride compound semiconductor refers to a semiconductor composed of a group III-V compound containing at least nitrogen as a group V element. That is, it is a III-V group compound semiconductor that contains a group III element such as Al, Ga, In, etc., and a group V element such as N, P, As, etc., and always contains N. For example, the composition formula is as follows.
Al_aGa_bIn_cN_dX_1-d
(0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, a + b + c = 1, 0 <d ≦ 1, X: Group V atoms such as P and As)
Further, a semiconductor in which a part of each constituent atom is replaced with an impurity atom or the like is also included.
[0002]
[Prior art]
Group III-V nitride compound semiconductors are attracting attention for use in semiconductor devices such as light-emitting elements in the ultraviolet to green wavelength region and power devices for power. In particular, in recent years, development of high-quality single crystal thin film manufacturing technology has been developed in III-V nitride compound semiconductors, and single crystal low resistance p-type layers have become possible. As a result, the practical application of light emitting diodes emitting light in the blue to green wavelength has been realized, and further development is expected.
[0003]
In the future, efforts are being made from various directions to improve the performance of light-emitting diodes that have been put to practical use and to realize semiconductor lasers that are expected to be put to practical use. One of these is the p-type contact layer. There is development of.
[0004]
For example, in a semiconductor device such as a light emitting diode or a semiconductor laser that has excellent ohmic properties, low contact resistance, and requires a low resistance contact layer, the characteristics are the performance of the semiconductor device, for example, low voltage operation, It has a great influence on high brightness, high reliability, and long life.
[0005]
As a conventional technique, for example, a technique disclosed in JP-A-8-97471 is known. In this technique, two layers having different Mg impurity concentrations are formed, and a layer having a high Mg impurity concentration and a layer having a low Mg impurity concentration are arranged from the side close to the positive electrode.
[0006]
In the embodiment, for example, the Mg impurity concentration is close to the positive electrode, and the concentration is 2 × 10.²⁰[/ Cm^ThreeThe layer thickness is 50 nm, while the Mg impurity concentration is low and the concentration is 1 × 10²⁰[/ Cm^Three], A structure having a layer thickness of 0.2 μm is shown. The layer with a low Mg impurity concentration is a layer mainly for efficiently injecting holes into the active layer, and the layer with a high Mg impurity concentration mainly serves as a layer for making ohmic contact with the positive electrode. It is thought that
[0007]
[Problems to be solved by the invention]
However, the conventional techniques described above are still insufficient for the characteristics required for various semiconductor devices, that is, ohmic characteristics, contact resistance, and series resistance. For this reason, problems remain in the performance of the semiconductor device, for example, low voltage operation, high brightness, high reliability, and long life.
[0008]
Because of the magnitude of the resistance of the p-type contact layer itself and the contact resistance of the positive electrode, the operating voltage becomes high, and because of the heat generated in that portion, the crystallinity of the p-type contact layer is poor, The device tends to deteriorate. For example, in a light-emitting diode manufactured using a conventional technique, a reliability test was performed. As a result, the majority of the elements had a light emission intensity that fell below the half-value of the initial value or became inoperable.
[0009]
Accordingly, an object of the present invention is to provide a p-type contact layer that is excellent in ohmic property with respect to the positive electrode, has low contact resistance, and has low resistance.
[0010]
[Means for Solving the Problems]
  In the present invention, as a method for solving the above-mentioned object, in order to reduce the contact resistance, the acceptor impurity concentration of the p-type contact layer in the portion in contact with the positive electrode is set to 3 × 10.¹⁹~ 5x10^{twenty one}[/ Cm^ThreeIn the p-type contact layer, the acceptor impurity concentration is continuously decreased from the side in contact with the positive electrode toward the opposite side.The acceptor impurity concentration of the portion of the p-type contact layer that is in contact with the layer opposite to the positive electrode is 1 × 10 ¹⁸ ~ 3x10 ¹⁹ [/ Cm ^Three ]ageing.
[0012]
  In the present invention, the decrease in acceptor impurity concentration in the p-type contact layer is preferably exponential or linear..
[0014]
  TheFurthermore, in the present invention, it is desirable that the acceptor impurity of the p-type contact layer is Mg.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
In the present embodiment, a light-emitting diode of a III-V nitride compound semiconductor was manufactured using the present invention. Using a MOCVD apparatus, the source gas is trimethylgallium, trimethylaluminum, trimethylindium as an organometallic compound containing a group III element, ammonia as a hydride containing a group V element, and biscyclohexane as an acceptor impurity as an impurity source gas. A semiconductor layer was grown using pentadienylmagnesium and silane as the donor impurity.
[0016]
FIG. 1 shows a cross-sectional view of a pn junction type light emitting diode having a DH structure manufactured in this embodiment. The structure is as shown below. For example, on a substrate 11 such as sapphire, a GaN low-temperature buffer layer 12, a Si-doped GaN layer 13, an Si-doped AlGaN layer 14 as an n-type cladding layer, an InGaN active layer 15, and an Mg-doped AlGaN layer 16 as a p-type cladding layer. The Mg-doped GaN layer 17 is laminated, and the Mg-doped GaN layer 18 as a p-type contact layer in contact with the positive electrode is laminated thereon.
[0017]
Further, a part from the Mg-doped GaN layer 18 to the Si-doped GaN layer 13 is etched until the Si-doped GaN layer 13 is exposed on the surface, and the positive electrode layer 20 and the Si-doped GaN layer 13 are formed on the Mg-doped GaN layer 18. A negative electrode layer 21 is formed thereon.
[0018]
The manufacturing method is shown below. FIG. 2 is a cross-sectional view of the semiconductor device showing a manufacturing process of the semiconductor device in the present embodiment.
[0019]
First, the gallium nitride III-V compound semiconductor multilayer structure shown in FIG. 2A is formed.
First, the cleaned substrate 11 is introduced into the MOCVD apparatus, and H₂Cleaning is performed at a substrate temperature of 1100 ° C. in an atmosphere of carrier gas. Subsequently, the substrate temperature is set to 600 ° C., trimethylgallium and ammonia are used as source gases, and H₂Was introduced into the reactor as a carrier gas, and a GaN low-temperature buffer layer 12 was grown on the substrate 11 by 30 nm. Then, the substrate temperature is set to 1050 ° C., trimethylgallium, ammonia, and silane are used as source gases, and H₂Was introduced into the reactor as a carrier gas, and a Si-doped GaN layer 13 was grown on the GaN low-temperature buffer layer 12 by 4 μm. The Si impurity concentration of this GaN layer is 5 × 10.¹⁸[/ Cm^Three]Met.
[0020]
Next, the substrate temperature is set to 1050 ° C., trimethylgallium, trimethylaluminum, ammonia, and silane are used as source gases, and H₂Was introduced into the reactor as a carrier gas, and an Si-doped AlGaN layer 14 having an Al composition of 0.1 was grown as an n-clad layer on the Si-doped GaN layer 13 by 0.1 μm. The Si impurity concentration of this AlGaN layer is 5 × 10.¹⁷[/ Cm^Three]Met. Thereafter, the substrate temperature is set to 750 ° C., and trimethylgallium, trimethylindium, and ammonia are used as source gases, and N₂Was introduced into the reactor as a carrier gas, and an InGaN active layer 15 having an In composition of 0.3 was grown on the n-type Si-doped AlGaN layer 14 by 2 nm.
[0021]
Then, the substrate temperature is set to 1050 ° C., trimethylgallium, trimethylaluminum, ammonia, biscyclopentadienylmagnesium is used as a source gas, and H₂Was introduced into the reactor as a carrier gas, and an Mg-doped AlGaN layer 16 having an Al composition of 0.1 was grown as a p-cladding layer on the InGaN active layer 15 by 0.1 μm. The Mg impurity concentration of this AlGaN layer is 1 × 10.¹⁹[/ Cm^Three]Met. Further, the substrate temperature is set at 1050 ° C., trimethylgallium, ammonia, biscyclopentadienylmagnesium is used as a source gas, and H₂Was introduced into the reactor as a carrier gas, and an Mg-doped GaN layer 17 was grown on the Mg-doped AlGaN layer 16 by 0.3 μm. Note that the Mg impurity concentration of the GaN layer is 1 × 10.¹⁹[/ Cm^Three]Met. In order to control the Mg impurity concentration, the flow rate of the raw material biscyclopentadienyl magnesium may be controlled. In this case, for example, the flow rate of biscyclopentadienylmagnesium was 0.02 μmol / min.
[0022]
Further, the substrate temperature is set at 1050 ° C., trimethylgallium, ammonia, biscyclopentadienylmagnesium is used as a source gas, and H₂Was introduced into the reactor as a carrier gas, and an Mg-doped GaN layer 18 was grown on the Mg-doped GaN layer 17 as a p-type contact layer in contact with the positive electrode by 30 nm. The Mg impurity concentration of this GaN layer is 5 × 10.²⁰[/ Cm^Three]Met. At this time, the flow rate of biscyclopentadienylmagnesium, which is an Mg source gas, is 1.00 μmol / min, which is higher than when the Mg-doped GaN layer 17 is grown. Subsequently, the obtained semiconductor laminated structure is, for example, N₂The Mg-doped AlGaN layer 16, the Mg-doped GaN layer 17, and the Mg-doped GaN layer 18 were reduced in resistance by thermal annealing at 800 ° C. in an atmosphere.
[0023]
Next, as shown in FIG. 2B of the semiconductor laminated structure, a photoresist film 22 is attached to the semiconductor surface, and a part thereof is removed by photolithography. Then, etching is performed by RIE (reactive ion etching) using the remaining photoresist film as a mask until the Si-doped GaN layer 13 is exposed from the Mg-doped GaN layer 18 until a part of the Si-doped GaN layer 13 is exposed to the surface. Etch.
[0024]
Thereafter, the photoresist film is peeled off, and a Ti / Al negative electrode layer 21 is formed on the Si-doped GaN layer 13 and a Ni / Au positive electrode layer 20 is formed on the Mg-doped GaN layer 18 as shown in FIG. A metal film is deposited to produce an electrode.
[0025]
The semiconductor laminated structure thus obtained can be divided by dicing or the like to obtain a light emitting diode chip.
When the characteristics of the LED chip obtained through the above steps were measured, an applied voltage of 3.4 V, a light emission wavelength of 450 nm, and a light emission output of 1.5 mW could be obtained when driven with a current of 20 mA.
[0026]
In addition, when a reliability test was conducted, about 80% of the devices had a light emission intensity of 90% or more compared to the initial light emission intensity after 1000 hours in a state where the operation current was 50 mA continuously at room temperature. there were.
[0027]
(Comparative example)
Next, as a comparative example, a case where the Mg-doped GaN layer 18 serving as a p-type contact layer in contact with the positive electrode is stacked as thick as 50 nm is shown.
Until the Mg-doped GaN layer 17 is grown, it is the same as the previous example, but the Mg-doped GaN layer 18 was grown with the layer thickness set to 50 nm instead of 30 nm. After that, a semiconductor device was manufactured by the same method as the above-described example.
[0028]
When the characteristics of the light emitting diode chip obtained in this step were measured, an applied voltage of 3.5 V, an emission wavelength of 450 nm, and an emission output of 1.3 mW were obtained when the current was driven at 20 mA. In addition, when a device manufactured using the conventional technique was subjected to a reliability test in the same manner as described above, 20% of the devices showed characteristics after the test of 90% or more of the initial characteristics. It was about.
[0029]
The above can be explained as follows.
When the GaN film is doped with Mg, the hole concentration changes depending on the concentration. When the Mg-doped GaN film is grown to 4 μm, the sample is subjected to thermal annealing for reducing the resistance, and the change in the hole concentration with respect to the Mg impurity concentration is examined as shown in FIG. Mg impurity concentration is 3 × 10¹⁹[/ Cm^ThreeIf the Mg impurity concentration is increased, the hole concentration after the low resistance annealing is increased accordingly. However, the Mg impurity concentration is 3 × 10¹⁹[/ Cm^Three] Above, even if the Mg impurity concentration is increased, the hole concentration does not increase, but the hole concentration tends to decrease. This is because the Mg impurity concentration is 3 × 10¹⁹[/ Cm^Three] Since it is highly doped, it indicates that many crystal defects enter and the hole concentration does not increase.
[0030]
Mg impurity concentration 3 × 10¹⁹[/ Cm^ThreeIn the above case, the hole concentration after the resistance-reducing annealing decreases with increasing Mg impurity concentration, indicating deterioration of the crystal, while the Mg impurity concentration is 3 × 10.¹⁹[/ Cm^ThreeIt was found that an ohmic contact can be easily made with respect to the positive electrode as compared with the case of less. Therefore, the Mg impurity concentration is 3 × 10¹⁹[/ Cm^ThreeThe above Mg-doped GaN film has high resistance as a contact layer, but it has been found that ohmic contact with the electrode is easy to take. The Mg impurity concentration is 5 × 10.^{twenty one}[/ Cm^Three], The crystallinity of GaN as a single crystal is impaired, and GaN having sufficient crystallinity cannot be obtained, which is not practical.
[0031]
However, the Mg impurity concentration is 3 × 10¹⁹[/ Cm^ThreeIt has been found that the phenomenon in which the hole concentration does not increase and the resistance is increased due to lattice defects is greatly dependent on the layer thickness. FIG. 4 also shows the correlation between the Mg impurity concentration and the hole concentration when the layer thickness is 30 nm.
[0032]
Further, FIG. 3 shows changes in device characteristics when the device is manufactured by changing the layer thickness of the Mg-doped GaN layer 18 as a contact layer in this structure. As can be seen from this figure, when the thickness exceeds 40 nm, the applied voltage increases and the light emission output decreases. It can be seen that the thickness of the p-type contact layer in contact with the positive electrode is preferably 40 nm or less.
[0033]
The result shown in FIG. 3 is considered to occur for the following reason. In the case of the impurity concentration as shown in this example, when the crystallinity was evaluated, it was found that there was a so-called critical film thickness in which the crystallinity rapidly deteriorated when a certain layer thickness was exceeded. This is thought to be because Mg as an impurity enters the lattice position of Ga, but Mg and Ga have different atomic radii, so that stress accumulates on the film itself due to doping. The evaluation by the present inventor confirmed that the crystallinity of the GaN film suddenly deteriorated when the layer thickness exceeded 40 nm. From this, as shown in the present embodiment, it is considered that the element characteristics are greatly changed by the change in the thickness of the contact layer.
In consideration of the series resistance component of the contact layer itself, the thinner the layer thickness, the smaller the series resistance.
[0034]
Furthermore, the efficiency with which light emitted from the active layer is extracted to the outside may vary depending on the thickness of the contact layer. As the layer thickness increases, the ratio of light extracted to the outside decreases, resulting in a decrease in light emission output.
[0035]
Considering the above comprehensively, the p-type contact layer has an Mg impurity concentration of 3 × 10 6.¹⁹~ 5x10^{twenty one}[/ Cm^Three], It was found that a group III-V nitride compound semiconductor film having a layer thickness of 40 nm or less may be used.
[0036]
As another embodiment, the Mg-doped GaN layer 17 has a layer thickness of 0.3 μm and an Mg impurity concentration of 5 × 10 5.¹⁸[/ Cm^ThreeThe Mg-doped GaN layer 18 which is a p-type contact layer has a layer thickness of 40 nm and an Mg impurity concentration of 5 × 10 5.¹⁹[/ Cm^ThreeThus, even when a light emitting diode is manufactured in the same manner, it can be confirmed that, for the same reason as described above, an element having better element characteristics can be obtained compared to an element manufactured using a conventional technique. It was.
[0037]
In this embodiment, Mg is used as the acceptor impurity. However, similar results can be obtained by using other impurities such as Zn, Cd, Be, and C.
[0038]
(Embodiment 2)
In this embodiment, a contact layer structure in which the Mg impurity concentration is continuously changed is produced as a p-type contact layer in contact with the positive electrode. A cross-sectional view of the light-emitting diode fabricated in this embodiment is shown in FIG. This laminated structure was produced as follows.
[0039]
First, up to the Mg-doped AlGaN layer 16 as the p-cladding layer was fabricated by the same method as in the previous embodiment. Next, subsequently, an Mg-doped GaN layer 30 was produced as a contact layer by the following method. The substrate temperature is set to 1050 ° C., trimethylgallium, ammonia, biscyclopentadienylmagnesium is used as a source gas, and H₂Was introduced into the reactor as a carrier gas, and an Mg-doped GaN layer 30 with a Mg impurity concentration continuously changing was grown on the Mg-doped AlGaN layer 16 by 0.3 μm. The Mg impurity concentration (y) of the Mg-doped GaN layer 30 is such that the direction perpendicular to the interface between the Mg-doped AlGaN layer 16 and the Mg-doped GaN layer 30 is the Z-axis, the interface is z = 0, and the direction of the Mg-doped GaN layer 30 is Is +, Y = 1 × 10 when Z = 0 μm¹⁸[/ Cm^Three], When z = 0.3 μm, y = 1 × 10²⁰[/ Cm^Three] In an exponential manner, that is, y = a × 10^{[b * z]}Increased doping in the form of In order to change such impurity concentration, it can be formed by continuously changing the gas flow rate of biscyclopentadienyl magnesium, which is a source gas of Mg impurities.
[0040]
A semiconductor multilayer structure was produced as described above, and then a light emitting diode was produced through the same process as in the previous embodiment. The characteristics of the light-emitting diode chip thus obtained were measured. As a result, an applied voltage of 3.4 V, a light emission wavelength of 450 nm, and a light emission output of 1.5 mW were obtained when the current was driven at 20 mA. In addition, the device manufactured in this embodiment was subjected to a reliability test in the same manner as in Embodiment 1. As a result, the device whose characteristics after the test showed 90% or more of the initial characteristics was 80% or more of the whole. there were.
[0041]
Further, as a method of changing the Mg impurity concentration, a light emitting diode was similarly manufactured by changing it in a minute step shape so as to change in a pseudo continuous manner. Specifically, the Mg impurity concentration of the portion in contact with the base layer opposite to the side in contact with the positive electrode of the p contact layer is set to 2 × 10.¹⁸[/ Cm^Three], The Mg impurity concentration of the portion in contact with the positive electrode is 5 × 10¹⁹[/ Cm^Three] So that the Mg impurity concentration in the p-type contact layer is 2 × 10 2 for each step of the layer thickness of 8 nm.¹⁸[/ Cm^Three] It was changed so as to increase. In this case as well, an element having better element characteristics can be obtained as compared with an element manufactured using the conventional technique described above.
[0042]
From the above, the following can be understood. As in this embodiment, in the contact layer in contact with the positive electrode, the impurity concentration on the active layer side is low, and the impurity concentration on the positive electrode side is increased so that the impurity concentration is continuously increased. An effect similar to that shown in the first embodiment can be obtained. In particular, in this case, it has been found that an increase in crystal defects in a layer having a high impurity concentration can be relatively suppressed as compared with a case where the impurity concentration is changed stepwise and steeply. For this reason, the contact layer can be grown relatively thick. In this way, if the deterioration of crystallinity can be suppressed even if the layer thickness of the high impurity concentration region is large, a relatively thick contact layer can be formed, and the current can be spread more in the lateral direction, so that the device characteristics are also good. become.
[0043]
From the data of Embodiment 1, the Mg impurity concentration in this contact layer is 3 × 10 in consideration of contact with the positive electrode in the highest concentration portion on the side in contact with the positive electrode.¹⁹~ 5x10^{twenty one}[/ Cm^Three1 × 10 in consideration of efficiently injecting holes into the active layer at the lowest concentration portion on the side opposite to the side in contact with the positive electrode¹⁸~ 3x10¹⁹[/ Cm^Three] Is desirable. Furthermore, the Mg impurity concentration is 3 × 10.¹⁹~ 5x10^{twenty one}[/ Cm^Three] The total layer thickness in the range is preferably 100 nm or less.
[0044]
In this embodiment, the Mg impurity concentration is increased exponentially, but may be changed in another function, for example, a linear function.
Further, as shown in the present embodiment, when the Mg impurity concentration continuously changes as a pseudo state, that is, even if the Mg impurity concentration changes stepwise by a minute change amount, The same effect as when changing is obtained. In this case, the ratio of the Mg impurity concentration between the layers in contact with each other is preferably 10 or less, the layer thickness of each layer is 40 nm or less, and the Mg impurity concentration is 3 × 10.¹⁹~ 5x10^{twenty one}[/ Cm^Three] The total layer thickness in the range is preferably 100 nm or less.
[0045]
(Embodiment 3)
In this embodiment, the Mg-doped GaN layer 40 that is a layer in which the Mg impurity concentration is periodically changed is introduced as the p-type contact layer in contact with the positive electrode. A cross-sectional view of the manufactured light emitting diode is shown in FIG. The Mg-doped GaN layer 40 has an Mg impurity concentration of 1 × 10¹⁹[/ Cm^ThreeThe Mg impurity low concentration layer 41 having a layer thickness of 3 nm and the Mg impurity concentration of 3 × 10²⁰[/ Cm^Three], A structure in which two layers of the Mg impurity high-concentration layer 42 having a layer thickness of 2 nm are set as one cycle and the cycle is repeated 20 times. Other layers were produced in the same manner as in the first embodiment.
[0046]
When the characteristics of the LED chip obtained through the above steps were measured, an applied voltage of 3.4 V, a light emission wavelength of 450 nm, and a light emission output of 1.5 mW could be obtained when driven with a current of 20 mA. In addition, the device manufactured in this embodiment was subjected to a reliability test in the same manner as in Embodiment 1. As a result, about 80% of the devices showed characteristics after testing that were 90% or more of the initial characteristics. It was.
[0047]
In another embodiment, the Mg impurity concentration is 1 × 10 6 as the structure of the p-type contact layer.¹⁹[/ Cm^ThreeThe Mg impurity low concentration layer 41 having a layer thickness of 40 nm and the Mg impurity concentration of 5 × 10²⁰[/ Cm^ThreeA structure in which two layers of the Mg impurity high-concentration layer 42 having a layer thickness of 4 nm are taken as one cycle and this was repeated 10 times was also produced.
[0048]
Also in this case, as in the previous embodiment, it was possible to obtain an element having better element characteristics as compared with an element manufactured using a conventional technique.
[0049]
Furthermore, as another embodiment, the Mg impurity concentration is 2 × 10 6 as the structure of the p-type contact layer.¹⁸[/ Cm^ThreeThe Mg impurity low concentration layer 41 having a layer thickness of 30 nm and the Mg impurity concentration of 5 × 10¹⁹[/ Cm^ThreeA structure in which two layers of the Mg impurity high-concentration layer 42 having a layer thickness of 10 nm are taken as one cycle and the cycle was repeated five times was also produced. Also in this case, as in the previous embodiment, it was possible to obtain an element having better element characteristics as compared with an element manufactured using a conventional technique.
[0050]
As still another embodiment, the Mg impurity concentration is 2 × 10 6 as the structure of the p-type contact layer.¹⁹[/ Cm^ThreeThe Mg impurity low concentration layer 41 having a layer thickness of 100 nm and the Mg impurity concentration of 1 × 10²⁰[/ Cm^ThreeA structure corresponding to a so-called one cycle by two layers of the Mg impurity high concentration layer 42 having a layer thickness of 20 nm was also produced. Also in this case, like the previous embodiment, an element having good element characteristics could be obtained.
[0051]
This shows the following. As in the present embodiment, the same effect as that of the first embodiment can be obtained by alternately stacking layers having a low impurity concentration and layers having a high impurity concentration. In this case, the layer having a high impurity concentration has a relatively large number of crystal defects, but the layer having a small thickness still has sufficient crystallinity. When a layer having a low impurity concentration is grown thereon, this layer has relatively few crystal defects and crystallinity is improved. For this reason, even if a layer having a high impurity concentration is further grown thereon, the crystallinity of this layer can suppress deterioration of the crystallinity as compared with the case where layers having a high impurity concentration are continuously stacked. Therefore, a contact layer with high crystallinity can be formed, and deterioration of element characteristics is not observed. From this, it was found that it is possible to form a contact layer that can easily make ohmic contact with the electrode with a large thickness.
[0052]
In this case, since the crystallinity can be recovered in the layer having a low Mg impurity concentration, the concentration ratio of the low concentration layer to the high layer varies the concentration of the acceptor impurity of the second embodiment in a pseudo and continuous manner. It can be made larger than the case of making it. From the data of Embodiment 1, the Mg impurity concentration in this contact layer is 1 × 10 at the low concentration portion.¹⁸~ 3x10¹⁹[/ Cm^Three] 3 × 10 in high density part¹⁹~ 5x10^{twenty one}[/ Cm^ThreeIt is desirable that Further, as shown in the first embodiment, the layer thickness of the high-concentration layer is deteriorated in device characteristics when the layer thickness is increased to some extent. For this reason, the thickness of one layer is desirably 40 nm or less.
Further, the number of periods is not limited to the numerical values shown in the present embodiment.
On the other hand, if the total thickness of the p-type contact layer exceeds 1 μm, the series resistance as an element increases, which causes a problem. Therefore, the total layer thickness of the p-type contact layer is desirably 1 μm or less. More desirably, it is 0.5 μm or less.
[0053]
In the embodiments described so far, it is an example of a light emitting diode. However, the present invention relates to a semiconductor device other than a light emitting element such as a light emitting diode or a semiconductor laser, for example, as a p-type contact layer of a light receiving element using a III-V group nitride compound semiconductor, or a group III-V nitride. As a base electrode of an npn bipolar transistor using a system compound semiconductor, it can be used for various semiconductor devices that require a p-type contact layer.
[0054]
【The invention's effect】
By using the present invention, the low voltage operation, high luminance, high reliability, and long life of the III-V nitride compound semiconductor device can be achieved.
[Brief description of the drawings]
1 is a structural cross-sectional view of a group III-V nitride-based compound semiconductor device manufactured by using the present invention shown in Embodiment 1. FIG.
2 is a diagram showing a manufacturing process of the III-V nitride compound semiconductor device manufactured by using the present invention shown in Embodiment 1. FIG.
FIG. 3 is a diagram showing a change in characteristics of a light emitting diode with respect to a layer thickness of a p-type contact layer in contact with a positive electrode.
FIG. 4 is a diagram showing the relationship between Mg impurity concentration and hole concentration in an Mg-doped GaN film.
5 is a structural cross-sectional view of a group III-V nitride-based compound semiconductor device manufactured by using the present invention shown in Embodiment 2. FIG.
6 is a structural sectional view of a group III-V nitride compound semiconductor device manufactured by using the present invention shown in Embodiment 3. FIG.
[Explanation of symbols]
11 Substrate
12 GaN low temperature buffer layer
13 Si-doped GaN layer
14 Si-doped AlGaN layer
15 InGaN active layer
16 Mg-doped AlGaN layer
17 Mg-doped GaN layer
18 Mg-doped GaN layer
20 Positive electrode layer
21 Negative electrode layer
22 Photoresist film
30 Mg-doped GaN layer
40 Mg-doped GaN layer
41 Mg impurity low concentration layer
42 Mg impurity high concentration layer

Claims (3)

A semiconductor device having a p-type layer, an n-type layer, and an active layer disposed between the p-type layer, the n-type layer, and a p-type contact layer that is in contact with the positive electrode. The acceptor impurity concentration of the outermost surface portion in contact with the positive electrode of the p-type contact layer is 3 × 10 ^{19 to} 5 × 10 ²¹ [/ cm ³ ], and the p-type contact layer is in contact with the positive electrode. The acceptor impurity concentration continuously decreases from the side toward the opposite side, and the acceptor impurity concentration in the portion of the p-type contact layer in contact with the layer opposite to the positive electrode is 1 × 10 ^{18 to} 3 × 10 6. ¹⁹ [/ cm ³ ] semiconductor device. 2. The semiconductor device according to claim 1, wherein the decrease in acceptor impurity concentration in the p-type contact layer is exponential or linear. The semiconductor device according to claim 1 or 2, wherein the acceptor impurity of the p-type contact layer is Mg.

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