JP4380956B2 - Semiconductor light emitting device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor light-emitting device having a double hetero structure in which an active layer is sandwiched between an n-type clad layer and a p-type clad layer, and a semiconductor light-emitting device capable of controlling a change in characteristics such as luminance to be small even over time due to energization It relates to the manufacturing method.
[0002]
[Prior art]
Conventional red semiconductor light emitting devices include, for example, an n-type cladding layer made of an n-type InGaAlP-based semiconductor material, an active layer made of an InGaAlP-based semiconductor material having a lower band gap energy than the cladding layer, and a p-type A p-type cladding layer made of an InGaAlP-based semiconductor material is epitaxially grown to form a light emitting layer forming portion having a double hetero structure.
[0003]
Further, a p-type window layer (current diffusion layer) made of an AlGaAs compound semiconductor (for example, Al mixed crystal ratio of 0.7) is provided on the surface, and an AlGaAs system having an Al mixed crystal ratio smaller than that of the window layer thereon. A protective layer made of a compound semiconductor (for example, a mixed crystal ratio of Al of 0.5) is provided. A p-side electrode and an n-side electrode are formed on the back surface of the semiconductor substrate via a contact layer made of GaAs at the center of the surface.
[0004]
This type of semiconductor light-emitting element is not preferable for use if the characteristic change such as luminance change is great with the passage of time due to energization. Therefore, high temperature energization of about 85 ° C., low temperature energization of about −45 ° C., 85 ° C., humidity 85% A reliability test is performed in which about 500 hours of high-temperature and high-humidity energization is performed. In this reliability test, it is required that characteristics such as luminance change fall within a certain range.
[0005]
[Problems to be solved by the invention]
As described above, there may be a large variation in characteristics such as a change in luminance over time due to energization. In addition, the luminance change has a variation in that the luminance increases or decreases with time, not in a fixed direction, but increases in some cases and decreases in some cases.
[0006]
The present invention has been made in view of such a situation, and it is a double-heterostructure semiconductor light emitting device in which an active layer is sandwiched between cladding layers, and it is possible to reduce a change in characteristics such as a luminance change over time due to energization. An object of the present invention is to provide a semiconductor light emitting device that can be manufactured and a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
In the semiconductor light-emitting device using an InGaAlP-based compound semiconductor, the present inventors have made extensive studies to minimize the phenomenon in which the characteristic variation in which the luminance increases or decreases with the passage of time due to energization is as small as possible. As a result, it has been found that a change in characteristics such as luminance due to energization has a very close correlation with the carrier concentration of the n-type cladding layer of the semiconductor light emitting device. As a result of further intensive studies, it was found that even if the carrier concentration is the same, if the activation rate is too small, characteristic fluctuations are likely to occur. Then, it has been found that by controlling the carrier concentration and the activation rate within a narrow range, characteristic variations such as luminance changes are less likely to occur even with time changes due to energization. Here, the activation rate means, for example, the ratio of the number of atoms effective as a carrier to the number of atoms incorporated as an n-type dopant in the semiconductor layer.
[0008]
That is, conventionally, it is considered that the carrier concentration of the n-type cladding layer is as large as possible, and the series resistance in the semiconductor layer is reduced, which contributes to the light emission efficiency. The larger the carrier concentration of the n-type cladding layer, the better. When a compound semiconductor is used, it is considered that there is no problem if the carrier concentration is about 2 × 10 ¹⁷ cm ⁻³ or more, and there has been no idea of limiting the carrier concentration of the n-type cladding layer to a narrow range. Further, little attention has been paid to the activation rate in relation to the characteristics. However, as described above, as a result of intensive studies by the present inventors, if the carrier concentration of the n-type cladding layer at the time of manufacture is too high, the luminance is increased by the reliability test, and the carrier concentration of the n-type cladding layer is increased. Is low, the luminance decreases due to the reliability test, and if the activation rate is too small, the luminance increases due to the reliability test, and the carrier concentration and the activation rate of the n-type cladding layer are very changed over time. The present inventors have found that this greatly affects.
[0009]
A semiconductor light emitting device according to the present invention comprises a semiconductor substrate made of GaAs , and is provided on the semiconductor substrate, and is made of In _0.49 (Ga _y Al _1-y ) _0.51 P (0.05 ≦ y ≦ 0.5), 0.1 to 1.5 [mu] m thick n-type cladding _{layer, in 0.49 (Ga z Al 1} -z) 0.51 consists P (0.5 ≦ z ≦ 1.0) , 0.1~1.5μm thickness of the active layers, and in consist _{0.49 (Ga y Al 1-y} ) 0.51 P (0.05 ≦ y ≦ 0.5), p -type cladding layer of 0.1~1.5μm thickness Ru is formed by sequentially growing A light-emitting layer forming portion, and provided on the light-emitting layer forming portion , made of Al _v Ga _1-v As (0.5 ≦ v ≦ 0.8), and a window layer having a thickness of 1 to 12 μm. A light-emitting diode that does not have a layer and emits light on the entire surface of the chip, and the carrier concentration of the n-type cladding layer is 2 × 10 ^{18 to} 2.5 × 10 ¹⁸ cm. ^-3, and, by activation rate of n-type dopant Ri der least 25%, the carrier concentration of the p-type cladding layer is to be a ^{5 × 10 16 ~2 × 10 18} cm -3, energization It is formed so as to suppress a change in luminance due to time .
[0010]
By adopting this structure, the carrier concentration and the activation rate of the n-type cladding layer are strictly controlled, so that a change in characteristics such as a change in luminance can be suppressed to a very small value even with a time change due to energization. As a result, the reliability of the semiconductor light emitting element can be greatly improved.
[0011]
A method of manufacturing a semiconductor light emitting device according to the present invention includes: a light emitting layer forming portion in which an active layer made of an InGaAlP-based compound semiconductor is sandwiched between an n-type cladding layer and a p-type cladding layer having a larger band gap than the active layer on a semiconductor substrate made of GaAs was grown by MOCVD at no current confining layer, a method of a semiconductor light emitting device Ru emit light on the whole surface of the chip, on the semiconductor _{substrate, in 0.49 (Ga y Al 1} -y) 0.51 P ( the n-type cladding layer consisting of 0.05 ≦ y ≦ 0.5) to a thickness of _{0.1~1.5μm, in 0.49 (Ga z Al} 1-z) 0.51 P (0.5 ≦ z ≦ 1. 0) to a thickness of 0.1 to 1.5 μm, and a p-type cladding layer of In _0.49 (Ga _y Al _1-y ) _0.51 P (0.05 ≦ y ≦ 0.5) to 0 forming a light emitting layer forming portion by sequentially grown to a thickness of .1～1.5Myuemu, A window layer made of _{Al v Ga 1-v As (} 0.5 ≦ v ≦ 0.8) was formed to a thickness of 1~12μm on the light emitting layer forming portion, the growth of the n-type cladding layer, said semiconductor While controlling the temperature of the substrate with a radiation thermometer and controlling it within a temperature range within ± 5 ° C. of the predetermined temperature, the carrier concentration is 2 × 10 ^{18 to} 2.5 × 10 ¹⁸ cm ⁻³ and active The dopant supply amount and growth temperature are set so that the conversion rate is 25% or more, and the growth of the p-type cladding layer is performed so that the carrier concentration becomes 5 × 10 ¹⁶ to 2 × 10 ¹⁸ cm ^−3. It is characterized by suppressing the time change of the brightness | luminance by electricity supply. Here, the predetermined temperature is determined by the flow rate of the dopant gas to be introduced, the MOCVD apparatus, and the like, and indicates an optimum temperature for obtaining 2.25 × 10 ¹⁸ cm ⁻³ . That is, the optimum temperature for obtaining a desired carrier concentration can be changed depending on the apparatus and growth conditions, but the temperature of the semiconductor substrate during growth is controlled within a range of ± 5 ° C. from the optimum temperature.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, a semiconductor light emitting device and a method for manufacturing the same according to the present invention will be described with reference to FIG. In the semiconductor light emitting device according to the present invention, a light emitting layer forming part 11 made of an InGaAlP-based compound semiconductor is provided on a semiconductor substrate 1, and a window layer 6 is provided on the light emitting layer forming part 11, and a protective layer is formed on the surface thereof. 10 is provided, the carrier concentration of the n-type cladding layer 3 is controlled in the range of 2 × 10 ^{18 to} 2.5 × 10 ¹⁸ cm ⁻³ , and the activation rate of the n-type dopant is controlled to 25% or more. ing.
[0014]
The light emitting layer forming portion 11 is made of, for example, In _0.49 (Ga _y Al _1-y ) _0.51 P (0.05 ≦ y ≦ 0.5, for example, y = 0.33), and has a carrier concentration of 2 × 10 ¹⁸ to 2 .5 × 10 ¹⁸ cm ^-3 and about n-type cladding layer 3 is controlled to 25% or more activation rate 0.1 to 1.5 [mu] m, for example, the emission wavelength of about 570nm in _0.49 (Ga _z Al _1-z ) _0.51 P (0.5 ≦ z ≦ 1.0, for example, z = 0.7), the active layer 4 is about 0.1 to 1.5 μm, for example, In _0.49 (Ga _y Al _1-y ). _The p-type cladding layer 5 made of _0.51 P (0.05 ≦ y ≦ 0.5, for example, y = 0.33) and having a carrier concentration of 5 × 10 ¹⁶ to 2 × 10 ¹⁸ cm ⁻³ is 0.1. Each of them is grown up to about 1.5 μm. In addition, the semiconductor layer which comprises a light emitting layer formation part is not restricted to an InGaAlP type compound semiconductor, The semiconductor layer of other luminescent colors, such as an AlGaAs type compound semiconductor, can be used.
[0015]
A window made of Al _v Ga _1-v As (0.5 ≦ v ≦ 0.8) and having a carrier concentration of 1 × 10 ¹⁸ to 1 × 10 ²⁰ cm ⁻³ on the surface of the light emitting layer forming portion 11. The layer 6 is provided about 1 to 12 μm. The surface of the window layer _{6, Al t Ga 1-t} As protective layer 10 made of (0.3 ≦ t ≦ 0.6) is provided about 0.1 to 1 [mu] m, p-side electrodes thereon 8 A contact layer 7 made of GaAs or the like is provided only on the lower side, thereby forming a semiconductor laminated portion 12. As the semiconductor material of the protective layer 10, if Al _u In _1-u P (0.35 ≦ u ≦ 0.51), the band gap energy can be increased even if the Al mixed crystal ratio is decreased. Since the light can be extracted without losing the surface while suppressing the surface oxidation, it is more preferable in that the decrease in the emission luminance can be suppressed.
[0016]
The p-side electrode 8 may be formed, for example, by patterning after providing Au—Be / Ni / Mo / Au or the like over the entire surface, or by providing a mask in addition to the portion where the electrode is provided, It may be formed by a lift-off method in which the mask is removed after coating. On the back surface of the semiconductor substrate 1 made of GaAs, Au—Ge / Ni / Au or the like is provided on the entire surface to a thickness of about 0.3 μm, for example, and an n-side electrode 9 is formed.
[0017]
Next, the reason why the carrier concentration of the n-type cladding layer is in the range of 2 × 10 ^{18 to} 2.5 × 10 ¹⁸ cm ⁻³ and the activation rate of the n-type dopant is 25% or more will be described. As described above, the present inventors have made extensive studies to reduce the change over time of the characteristics due to the current test and the like, and as a result, the change over time in the characteristics has a very close relationship with the carrier concentration of the n-type cladding layer. I found out. That is, the semiconductor light emitting device having the structure shown in FIG. 1 is manufactured by changing the carrier concentration of the n-type cladding layer, and the other parts of the structure are manufactured under the same conditions. As a result of investigating the luminance change after operating the current for 20 hours at 20 mA which is twice as much, as shown in FIG. 2, it is almost proportional to the logarithm of the carrier concentration of the n-type cladding layer. I found it.
[0018]
The acceleration test for doubling the operating current is used for checking in a short time instead of performing the reliability test such as the above-described high-temperature energization and low-temperature energization for 500 hours. It has been confirmed that the permissible amount of change in luminance (± 30%) after the time and the permissible amount of change in luminance in the accelerated test are + 20% and −3%, corresponding to a substantially 1: 1 relationship. In addition, the carrier concentration is changed by increasing the flow rate of monosilane SiH ₄ which is a raw material gas of Si of the n-type dopant at a constant growth temperature (755 ° C.) when growing the n-type cladding layer. The carrier concentration was reduced by increasing the carrier concentration and decreasing the flow rate of monosilane SiH ₄ , which is the Si source gas for the n-type dopant. The carrier concentration was measured by CV measurement and Hall measurement.
[0019]
If the carrier concentration is too high, the initial light emission efficiency is low, and internal changes in the device occur when energized, and this change is considered to occur due to the improvement in light emission efficiency. If the carrier concentration is low, the luminance decreases. The reason for this is considered to be that the initial luminous efficiency is high but the luminous efficiency is lowered by energization.
[0020]
Therefore, from FIG. 2, if the n-type cladding layer is manufactured so that the carrier concentration is in the range of 2 × 10 ^{18 to} 2.5 × 10 ¹⁸ cm ⁻³ , the characteristics variation of the reliability test is almost satisfied. found. In order to satisfy this condition, the carrier gas concentration is controlled by adjusting the dopant gas during the growth of the n-type cladding layer to an appropriate constant amount, strictly controlling the temperature during the growth, and within a range of ± 5 ° C. Found that it can be strictly controlled.
[0021]
That is, as shown in FIG. 7, the relationship between the growth temperature when the carrier concentration is in the range of 2 × 10 ^{18 to} 2.5 × 10 ¹⁸ cm ⁻³ , the carrier concentration and the growth temperature are in a substantially proportional relationship, Since the absolute value of the growth temperature differs depending on the MOCVD apparatus, measuring instrument, measuring method, etc., the absolute value is not so meaningful, but in this example, the carrier concentration is set to 2.25 × 10 ¹⁸ cm ⁻³ . By controlling the temperature within the range of 750 to 760 ° C., ± 5 ° C., centering on 755 ° C. which is the optimum temperature for the carrier temperature, the carrier concentration is accurately within the range of 2 × 10 ^{18 to} 2.5 × 10 ¹⁸ cm ^−3. The reliability test results were within the predetermined range. In this case, the flow rate of the dopant gas SiH ₄ was constant at 5 sccm.
[0022]
Furthermore, as a result of intensive studies, the present inventors have also found that the change in characteristics has a close relationship with the growth temperature. That is, when the n-type cladding layer 3 is grown at 700 ° C. to change the carrier concentration variously, as shown in FIG. 3, the relationship between the carrier concentration of the n-type cladding layer and the luminance change is shown in FIG. It became different. This means that even with the same carrier concentration, the rate of change in luminance due to energization varies depending on the growth conditions, and even with the carrier concentration described above, satisfactory results are not necessarily obtained.
[0023]
Therefore, the carrier concentration of the n-type cladding layer is investigated, and the impurity concentration of Si, which is a dopant (impurity) atom incorporated in the semiconductor layer, is examined by SIMS analysis (secondary ion mass spectrometry). The activation rate of the dopant (carrier concentration / concentrated impurity concentration × 100 (%)) was calculated. FIG. 4 shows the results. Under the growth conditions shown in FIG. 2, the activation rate is 50% when the carrier concentration is between 2 × 10 ^{18 and} 2.5 × 10 ¹⁸ cm ^−3. Whereas the change is ˜40%, under the growth conditions shown in FIG. 3, the activation rate is 30% to 20% even when the carrier concentration is between 2 × 10 ^{18 and} 2.5 × 10 ¹⁸ cm ^−3. I can see that This indicates that the activation rate varies depending on the growth conditions even at the same carrier concentration.
[0024]
Therefore, the present inventors further changed the growth temperature and the flow rate of the dopant source gas SiH ₄ to grow under various conditions, and investigated the relationship between the carrier concentration and the activation rate. As a result, as shown in FIG. 5, when the growth is performed at a relatively high temperature, the flow rate of the source gas SiH ₄ and the carrier concentration are approximately proportional to each other, and the activation rate is high, whereas at a low temperature. It was found that when grown, the carrier concentration did not increase for the flow rate, and the activation rate decreased. In FIG. 5, the activation rate is displayed as “active X%” (X is a value of the activation rate). Then, a light emitting device having a changed activation rate in a state where the carrier concentration was made constant was manufactured, and a change in luminance with respect to the activation rate was examined. As a result, as shown in FIG. 6, it was found that the luminance increases as the activation rate decreases, and that the luminance change due to the acceleration test becomes significant when the activation rate is 25% or less. From this result, considering that the growth conditions change, it is necessary to manufacture not only the carrier concentration but also the activation rate of 25% or more. A range satisfying both of these is shown by hatching in FIG.
[0025]
According to the semiconductor light emitting device of the present invention, the carrier concentration of the n-type cladding layer and the activation rate of the dopant are controlled within a predetermined range. Even when a reliability test such as energization or high-temperature and high-humidity energization is performed, the variation in electrical characteristics such as luminance is controlled within a very small range, and a highly reliable semiconductor light emitting device can be obtained. It is necessary to control the carrier concentration and the activation rate of the n-type cladding layer. The p-type cladding layer has at least a low carrier concentration on the active layer side, and it does not change much over time due to energization. Since the n-type cladding layer contains a large amount of inert Si atoms, if the carrier concentration is too large, the initial light emission efficiency is low, causing an internal change of the element by energization, and the light emission efficiency is improved. It is considered that such a change occurs, the initial luminous efficiency is low, and it is activated by energization, so that the luminous efficiency is improved and the luminance is increased.
[0026]
Next, a manufacturing method of this semiconductor light emitting device will be described. For example, an n-type GaAs substrate 1 is placed in a MOCVD (metal organic chemical vapor deposition) apparatus, and reactive gases such as triethylgallium (TEG) or trimethylgallium (TMG), arsine (AsH ₃ ), phosphine (PH ₃ ), trimethylaluminum. Necessary gases of (TMA), trimethylindium (TMIn), SiH ₄ as an n-type dopant, and dimethyl zinc (DMZn) as a p-type dopant in the case of forming a p-type layer are introduced.
[0027]
First, while measuring the substrate temperature with a radiation thermometer, the temperature is strictly controlled to 755 ° C., and 5 sccm of the dopant gas SiH ₄ and necessary amounts of the reaction gases TMG, TMA, TMIn, and PH ₃ are introduced, respectively. The n-type cladding layer 3 made of In _0.49 (Ga _0.33 Al _0.67 ) _0.51 P is grown by about 0.3 to 1 μm while measuring the substrate temperature with a radiation thermometer so that the temperature change in the range of ± 5 ° C. (Growth time is about 20 minutes). Then, as in the case of manufacturing a normal semiconductor light emitting device, necessary reaction gas and dopant gas are introduced, and the active layer 4 made of non-doped In _0.49 (Ga _0.70 Al _0.30 ) _0.51 P as shown in FIG. The p-type cladding layer 5 made of In _0.49 (Ga _0.33 Al _0.67 ) _0.51 P is made about _0.3 to 1 μm, for example, the p-type window layer 6 made of Al _0.7 Ga _0.3 As is made 1 to 10 μm. The protective layer 10 made of Al _0.5 Ga _0.5 As is continuously grown to about 0.1 to 1 μm, and the contact layer 7 made of GaAs is continuously grown to about 0.2 to 1 μm.
[0028]
Thereafter, Au-Be / Ni / Mo / Au or the like is formed on the entire surface by lift-off method, mask vapor deposition, or patterning by photolithography method, and then the p-side electrode 8 is formed. An LED chip shown in FIG. 1 can be obtained by forming an n-side electrode 9 by providing Ge / Ni / Au or the like over the entire surface and forming a chip.
[0029]
【The invention's effect】
According to the present invention, since the carrier concentration of the n-type cladding layer is controlled within a narrow range, the change in characteristics such as luminance can be suppressed to a very small value even with the passage of time due to energization. As a result, a highly reliable semiconductor light emitting device can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an example of a cross-sectional structure of a semiconductor light emitting device according to the present invention.
FIG. 2 is a diagram showing a relationship of luminance change due to energization with respect to carrier concentration of an n-type cladding layer.
FIG. 3 is a diagram showing a relationship of luminance change due to energization with respect to a carrier concentration of an n-type cladding layer.
FIG. 4 is a diagram showing the relationship of the activation rate with respect to the carrier concentration of the n-type cladding layer.
FIG. 5 is a diagram showing the relationship between the carrier concentration, activation rate, and growth temperature of an n-type cladding layer.
FIG. 6 is a diagram showing a relationship of luminance change due to energization with respect to the activation rate of the n-type cladding layer.
FIG. 7 is a diagram showing a relationship between a desired carrier concentration and a growth temperature.
[Explanation of symbols]
3 n-type cladding layer 4 active layer 5 p-type cladding layer 11 light emitting layer forming part

Claims (2)

A semiconductor substrate made of GaAs, and provided on the semiconductor substrate, made of In _0.49 (Ga _y Al _1-y ) _0.51 P (0.05 ≦ y ≦ 0.5), having a thickness of 0.1 to 1.5 μm. the n-type cladding layer made of _{in 0.49 (Ga z Al 1-} z) 0.51 P (0.5 ≦ z ≦ 1.0), 0.1~1.5μm thickness active layer, and an in _0.49 (Ga _y A light emitting layer forming portion formed by sequentially growing a 0.1-1.5 μm-thick p-type cladding layer made of Al _1-y ) _0.51 P (0.05 ≦ y ≦ 0.5), and the light emission Provided on the layer forming portion, made of Al _v Ga _1-v As (0.5 ≦ v ≦ 0.8), made of a window layer having a thickness of 1 to 12 μm, and having no current confinement layer, A light-emitting diode that emits light on the entire surface, wherein the n-type cladding layer has a carrier concentration of 2 × 10 ^{18 to} 2.5 × 10 ¹⁸ cm ⁻³ , and an n-type dopant activity A semiconductor light emitting device that suppresses a change in luminance over time due to energization by having a conversion rate of 25% or more and a carrier concentration of the p-type cladding layer being 5 × 10 ¹⁶ to 2 × 10 ¹⁸ cm ⁻³ . A light-emitting layer forming portion is formed by MOCVD on a semiconductor substrate made of GaAs and an active layer made of an InGaAlP-based compound semiconductor is sandwiched between an n-type cladding layer and a p-type cladding layer having a larger band gap than the active layer, and a current confinement layer in no, a process for preparing a semiconductor light-emitting device Ru emit light on the whole surface of the chip, on the semiconductor _{substrate, in 0.49 (Ga y Al 1} -y) 0.51 P (0.05 ≦ y ≦ 0.5) the n-type cladding layer to a thickness of 0.1~1.5μm consisting active layer composed of _{in 0.49 (Ga z Al 1-} z) 0.51 P (0.5 ≦ z ≦ 1.0) 0.1 A p-type cladding layer made of In _0.49 (Ga _y Al _1-y ) _0.51 P (0.05 ≦ y ≦ 0.5) is formed to a thickness of 0.1 to 1.5 μm. forming a light emitting layer forming portion by sequentially growing, Al _v Ga _1-v As to the light emitting layer forming portion on A window layer composed of 0.5 ≦ v ≦ 0.8) formed to a thickness of 1～12Myuemu, the growth of the n-type cladding layer, while the temperature of the semiconductor substrate is measured by a radiation thermometer, a predetermined temperature The dopant is supplied so that the carrier concentration is 2 × 10 ^{18 to} 2.5 × 10 ¹⁸ cm ⁻³ and the activation rate is 25% or more by controlling the temperature within ± 5 ° C. The amount of growth and the growth temperature are set, and the growth of the p-type cladding layer is formed so that the carrier concentration is 5 × 10 ¹⁶ to 2 × 10 ¹⁸ cm ⁻³ , thereby suppressing the temporal change in luminance due to energization. A method for producing a semiconductor light-emitting element.

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