JP4935591B2 - Method for fabricating group III nitride semiconductor optical device and method for measuring photoluminescence spectrum - Google Patents

Description

  The present invention relates to a method for producing a group III nitride semiconductor optical device and a method for measuring a photoluminescence spectrum.

  Non-Patent Document 1 describes a high-power InGaN-based light emitting diode fabricated on a sapphire substrate. In Figure 2 of Non-Patent Document 1, the photoluminescence spectrum is evaluated to evaluate the light emitting diode epitaxial layer fabricated on the sapphire substrate.

Non-Patent Document 2 describes the fabrication of gallium nitride free-standing substrates. A gallium nitride free-standing substrate having a size exceeding 2 inches was fabricated by the HVPE method using a GaAs substrate as a starting substrate. The GaAs substrate is dissolved in aqua regia, and the thickness of the gallium nitride free-standing substrate is 500 μm.
phys.stat.sol. (a) 200, No.1, 95-98 (2003) Jpn. J. Appl. Phys. Vol. 40 (2001) pp.L140-L143 Part 2, No. 2B, 15 February 2001

  A substrate having a non-specular back surface is used to fabricate a group III nitride semiconductor optical device, and a semiconductor stack including a plurality of semiconductor layers is grown on the main surface of the mirror surface of the substrate. In order to evaluate the crystal quality of the semiconductor stack, the photoluminescence spectrum of the semiconductor layer of the semiconductor stack is measured.

  Although the photoluminescence spectral intensity reflects the crystal quality of the semiconductor layer of the semiconductor stack, according to the inventors' knowledge, the electrical properties of group III nitride semiconductor optical devices fabricated using similar semiconductor stacks When the measured value of the characteristic is compared with the above spectral intensity, the spectral intensity may not always accurately indicate the characteristic of the group III nitride semiconductor optical device. That is, the fluctuation of the spectrum intensity is influenced not only by the fluctuation of the growth condition but also by others. Under such circumstances, the inventors have made a study, and thus the present invention has been achieved.

  An object of the present invention is to provide a method for manufacturing a group III nitride semiconductor optical device having good device characteristics by accurately measuring photoluminescence spectrum intensity, and to provide a method for measuring a photoluminescence spectrum The purpose is to do.

  One aspect of the present invention is a method of fabricating a group III nitride semiconductor optical device. In this method, (a) a step of disposing a semiconductor substrate having a major mirror surface and a non-mirror rear surface in a growth apparatus; and (b) a semiconductor stack including first and second gallium nitride based semiconductor regions. Forming a substrate product for the group III nitride semiconductor optical device by growing on the main surface of the semiconductor substrate with the growth apparatus; and (c) irradiating the substrate product with excitation light. Measuring a photoluminescence spectrum including the first and second components from the first and second gallium nitride based semiconductor regions, respectively, and (d) the first component of the photoluminescence spectrum and the step Generating a ratio with the second component; and (e) comparing the predetermined value indicating the quality of the second gallium nitride based semiconductor region with the ratio and producing the substrate based on the result of the comparison The process of sorting things For example, the first gallium nitride based semiconductor region is provided between the semiconductor substrate and the second gallium nitride based semiconductor region.

  The present invention is also a method for measuring a photoluminescence spectrum of a gallium nitride based semiconductor region. In this method, (a) first and second gallium nitride based semiconductor regions grown on the main surface on a semiconductor substrate having a mirror surface and a non-mirror surface are irradiated with excitation light; Measuring a photoluminescence spectrum including the first and second components from the first and second gallium nitride based semiconductor regions, respectively, and (b) the first component of the photoluminescence spectrum and the first component. Generating a ratio with a component of 2 as a value indicating the quality of the second gallium nitride semiconductor region, wherein the first gallium nitride semiconductor region and the second gallium nitride semiconductor region It is provided between the semiconductor substrates.

  In these methods, the photoluminescence spectrum intensity of a substrate product using a substrate having a non-specular back surface is affected by reflection from the back surface. The influence of this reflection changes according to the fluctuation of the roughness of the back surface. Further, not only the crystal growth conditions but also the amount of light reflected from the back surface of the substrate varies. However, according to this method, not only the second component from the second gallium nitride semiconductor region but also the spectral intensity of the first component from the first gallium nitride semiconductor region is measured. The effect of reflection is reduced by using the ratio between the first and second components of the spectrum. Because both the light traveling from the first and second gallium nitride based semiconductor regions toward the substrate is reflected by the back surface of the substrate, the reflection components of these lights similarly include the influence of the back surface of the substrate. This is because the light is superposed on the light directly observed from these gallium nitride based semiconductor regions. Therefore, the crystal quality of the second gallium nitride based semiconductor region that affects the characteristics of the semiconductor light emitting device can be accurately evaluated.

  In the present invention described above, the second gallium nitride based semiconductor region may have a multiple quantum well structure. Since the multi-quantum well structure includes a plurality of well layers and a barrier layer, the composition and / or film thickness of these layers are factors that change the spectral intensity. According to the present invention, the influence of the reflected light from the back surface on the spectrum from the multiple quantum well structure can be reduced.

  In the present invention described above, the first gallium nitride based semiconductor region is preferably composed of a single semiconductor layer. According to the present invention, since the first gallium nitride based semiconductor region is used for monitoring the amount of light reflected from the back surface of the substrate, the first gallium nitride based semiconductor region is less likely to cause a change in spectral intensity. preferable. For this reason, it is preferable not to have a relatively complicated structure such as a quantum well structure but to consist of a single semiconductor layer.

  In the present invention, the peak wavelengths of the first and second components from the first and second gallium nitride based semiconductor regions are preferably both larger than the band gap wavelength of the semiconductor substrate. According to the present invention, both spectrum light from the first and second gallium nitride based semiconductor regions passes through the substrate and is reflected by the back surface of the substrate. In the present invention, the peak wavelength of the second component is preferably larger than the peak wavelength of the first component. According to the present invention, spectral light from the second gallium nitride based semiconductor region is not absorbed regardless of the film thickness of the first gallium nitride based semiconductor region. Therefore, not only the spectral light from the first gallium nitride based semiconductor region but also the spectral light from the second gallium nitride based semiconductor region is reflected by the back surface of the substrate.

  In the present invention, the semiconductor substrate may be a group III nitride substrate. The group III nitride substrate can be made of, for example, GaN, AlGaN, AlN, or the like.

  The present invention may further include a step of forming an electrode for the group III nitride semiconductor optical device after the substrate product is selected. According to the present invention, it is possible to reduce the burden of metallization by excluding substrate products whose spectral intensity does not reach a desired value. In addition, a group III nitride semiconductor optical device can be manufactured by changing the selection criteria according to the characteristics desired for the group III nitride semiconductor optical device.

  In the present invention described above, the second gallium nitride based semiconductor region preferably includes a light emitting layer for the group III nitride semiconductor optical device. ADVANTAGE OF THE INVENTION According to this invention, the crystal quality of the light emitting layer which affects the characteristic of a semiconductor light emitting element can be evaluated with sufficient precision.

  In the present invention, it is preferable that the first gallium nitride based semiconductor region is adjacent to the light emitting layer.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, there is provided a method for measuring a photoluminescence spectrum intensity with high accuracy to produce a group III nitride semiconductor optical device having good device characteristics, and for obtaining a photoluminescence spectrum. A method for measuring is provided.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, an embodiment relating to a method for producing a group III nitride semiconductor optical device and a method for measuring a photoluminescence spectrum of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

  FIG. 1 is a drawing showing a process flow of a method for producing a group III nitride semiconductor optical device and a method for measuring a photoluminescence spectrum according to an embodiment of the present invention. 2, 3 and 4 are schematic views schematically showing main steps of a method for producing a group III nitride semiconductor optical device and a method for measuring a photoluminescence spectrum.

  For example, a light-emitting diode (LED) will be described as a group III nitride semiconductor optical device with reference to FIG. In step S101, as shown in FIG. 2A, a substrate 11 used for crystal growth for preparing an LED structure is prepared. The substrate 11 is a semiconductor substrate and is made of a group III nitride such as GaN, AlGaN, AlN, or the like. The substrate 11 has a first surface 11a and a second surface 11b opposite to the first surface 11a. The roughness of the first surface 11a is sufficiently smaller than the roughness of the second surface 11b, and the roughness of the first surface 11a is such that a sufficiently good semiconductor crystal can be grown in the subsequent crystal growth. In a preferred embodiment, the first surface 11a is a mirror surface and the second surface 11b is a non-mirror surface. The mirror surface has, for example, an average square root roughness RMS (Root Mean Square) value of 10 nm or less in a range of 10 μm × 10 μm, and the non-mirror surface RMS is 120 nm or more. The substrate 11 is placed on a stage 13a of a growth apparatus 13 for forming a semiconductor stack. For example, in the case of a GaN substrate, the surface of the GaN substrate is mirror-finished, and the back surface of the GaN substrate is not mirror-finished for cost reduction, and is a non-mirror surface. However, there is no problem in the crystal growth process. It is a flat surface. The GaN substrate used in this embodiment is produced by slicing a GaN thick film grown by the HVPE method on a GaAs substrate on which an insulating film mask pattern made of, for example, silicon oxide is formed. Processing for mirror polishing (grinding, polishing, etching, etc.) is not performed on the back surface of the GaN substrate.

  As shown in FIG. 2B, in step S <b> 102, the semiconductor stack 15 is formed on the substrate 11 disposed in the growth apparatus 13. The semiconductor stack 15 includes a first gallium nitride based semiconductor region (hereinafter referred to as “first GaN based semiconductor region”) 17 and a second gallium nitride based semiconductor region (hereinafter referred to as “second GaN based semiconductor region”). 19). The first GaN-based semiconductor region 17 is provided between the second GaN-based semiconductor region 19 and the substrate 11. In order to monitor fluctuations in crystal growth conditions in the LED manufacturing process, the crystal quality of the second GaN-based semiconductor region 19 is measured by a photoluminescence spectrum (hereinafter referred to as “PL spectrum”). The first GaN-based semiconductor region 17 is used to assist the above monitoring. In a preferred embodiment, the second GaN-based semiconductor region 19 preferably includes a light emitting layer for a group III nitride semiconductor optical device. The crystal quality of the light emitting layer that affects the characteristics of the semiconductor light emitting device can be accurately evaluated.

  In this embodiment, the semiconductor stack 15 is made of a buffer layer 21 made of a gallium nitride semiconductor, an electron block layer 23 made of a gallium nitride semiconductor, and a gallium nitride semiconductor in addition to the GaN semiconductor regions 17 and 19 described above. A contact layer 25 can be included. In this manner, the semiconductor stack 15 is grown on the substrate main surface 11a to form the substrate product E1 for the group III nitride semiconductor optical device.

In step S <b> 103, the substrate product E <b> 1 is irradiated with the excitation light L _EX and the PL spectrum is measured by the PL measuring device 31. As shown in FIG. 3A, the first and second GaN-based semiconductor regions 17 and 19 grown on the main surface 11a of the substrate 11 are irradiated with excitation light L _EX for PL spectrum measurement. Therefore, the PL spectrum includes not only the second component L _OUT2 from the second GaN-based semiconductor region 19 but also the first component L _OUT1 from the first GaN-based semiconductor region 17. The second component L _OUT2 includes a direct component L (D) _OUT2 and a reflective component L (R) _OUT2 , and as shown, the reflective component L (R) _OUT2 is on the non-specular back surface 11b of the substrate 11. Generated by reflection. Therefore, the second component L _OUT2 to be measured includes not only the direct component L (D) _OUT2 but also a reflection component L (R) _OUT2 that varies depending on the reflectance of the non-specular back surface. For this reason, the change in the PL spectral intensity of the second component L _OUT2 is not always caused by the fluctuation in the manufacturing process of the second GaN-based semiconductor region 19.

Similarly to the second component, the first component L _OUT1 also includes a direct component L (D) _OUT1 and a reflection component L (R) _OUT1 , and as shown, the reflection component L (R) _OUT1 is a substrate. 11 is reflected and generated on the back surface of the non-mirror surface. Therefore, the first component L _OUT1 to be measured is not only the direct component L (D) _OUT1 but also the reflection component L (R) _{OUT1 that} varies depending on the reflectance of the back surface of the non-specular surface, in the same manner as the second component. Including. For this reason, the PL spectral intensity of the first component L _OUT1 varies depending on the reflectance of the back surface of the non-specular surface although it depends on the film forming condition variation in the manufacturing process of the first GaN-based semiconductor region 17.

After the measurement of the PL spectrum, in step S104, a ratio between the first component L _OUT1 and the second component L _OUT2 of the PL spectrum intensity (for example, peak intensity) is generated.

  As already described, the PL spectrum intensity of the substrate product E1 using the substrate 11 having the non-mirror-like back surface is affected by reflection from the back surface 11b. The influence of this reflection increases as the roughness of the back surface 11b increases. In addition to the crystal growth conditions, the amount of light reflected from the substrate back surface 11b varies.

In step S105, a ratio between the first component L _OUT1 and the second component L _OUT2 of the PL spectrum is generated. This ratio is used as a value indicating the quality of the second GaN-based semiconductor region 19. In the LED manufacturing process, the ratio (for example, L _OUT2 / L _OUT1 ) is compared with a predetermined value indicating the quality of the second GaN-based semiconductor region 19. A substrate product E1 is selected based on the result of the comparison.

As described above, not only the second component L _OUT2 from the second GaN-based semiconductor region 19 but also the spectral intensity of the first component L _OUT1 from the first GaN-based semiconductor region 17 is measured. The effect of reflection from is reduced by using the ratio of the first component L _OUT1 and the second component L _OUT2 of the spectrum. Because both the light traveling from the first and second GaN-based semiconductor regions 17 and 19 toward the substrate 11 is reflected by the back surface 11b of the substrate 11, the reflected light is similarly affected by the back surface 11b of the substrate 11. This is because they are superimposed on the light directly observed from these gallium nitride based semiconductor regions 17 and 19. Therefore, the crystal quality of the second gallium nitride based semiconductor region 19 that affects the optical characteristics of the LED can be accurately evaluated.

In the embodiment, the peak wavelengths of the first and second components L _OUT1 and L _OUT2 from the first and second GaN-based semiconductor regions 17 and 19 are preferably larger than the band gap wavelength of the semiconductor substrate. Both PL spectrum lights from the first and second GaN-based semiconductor regions 17 and 19 pass through the substrate 11 without being absorbed and are reflected by the substrate back surface 11b. The reflected light passes through the substrate 11 and the first and second GaN-based semiconductor regions 17 and 19 and is emitted from the epitaxial substrate E1. A detector for measurement detects this emitted light.

The peak wavelength of the second component _{L OUT2} is preferably greater than the peak wavelength of the first component _{L OUT2.} The PL spectrum light from the second GaN-based semiconductor region 19 is not absorbed regardless of the film thickness of the first GaN-based semiconductor region 17. Therefore, not only the PL spectrum light from the first GaN-based semiconductor region 17 but also the PL spectrum light from the second GaN-based semiconductor region 19 passes through the first GaN-based semiconductor region 17 and reaches the back surface 11 b of the substrate 11. To reach.

The reference LED structure as shown in FIG. 5 includes an epitaxial film structure fabricated on an n-type GaN substrate having a non-specular back surface, the epitaxial film structure comprising a first GaN-based layer 17. Not included. For this reason, the observed second component L _OUT2 includes not only the direct component L (D) _OUT2 but also the reflection component L (R) _OUT2 . _Whether or not there is an influence of the reflection component L (R) _OUT2 cannot be known.

  Referring to FIG. 1 again, in step S106, if necessary, the selected epitaxial substrate E1 is processed in the next step. Examples of this process include other inspection processes such as X-ray measurement and carrier concentration measurement, crystal growth, etching, film formation, and cleaning.

  In step S107, if necessary, the non-specular back surface 11b is processed on the selected epitaxial substrate E1. Specifically, the back surface 11b of the substrate 11 is polished or ground to produce the epitaxial substrate E2 including the substrate 11d. As shown in FIG. 3B, the substrate 11d has a back surface 11e having a roughness smaller than that of the back surface 11b.

  After the selection of the substrate product such as the epitaxial substrate E2, in step S108, electrodes 33a and 33b for the group III nitride semiconductor optical device are formed. As shown in FIG. 4, the electrode 33a (for example, anode) is formed on the contact layer 25 of the epitaxial substrate E2, and the electrode 33b (for example, cathode) is formed on the back surface 11e of the substrate 11d. According to this method, the burden of metallization can be reduced by excluding substrate products whose PL spectrum intensity does not reach a desired value. In addition, a group III nitride semiconductor optical device can be manufactured by changing the selection criteria according to the characteristics desired for the group III nitride semiconductor optical device.

  As shown in FIG. 2B, for example, the second GaN-based semiconductor region 19 can have a multiple quantum well structure 27. Since the multiple quantum well structure 27 includes a plurality of well layers 27a, barrier layers 27b, and barrier layers (and / or guide layers 27c), the composition and / or film thickness of these layers is a factor that varies the spectral intensity. It is. The influence which the reflected light from the back surface 11b has on the PL spectrum from the multiple quantum well structure 27 can be reduced.

  The first GaN-based semiconductor region 17 is preferably composed of a single semiconductor layer. Since the first GaN-based semiconductor region 17 is used to monitor the amount of light reflected from the substrate back surface 11 b, it is preferable that the first GaN-based semiconductor region 17 has a small factor for changing the PL spectrum intensity. For this reason, it is preferable not to have a relatively complicated structure such as the quantum well structure 27 but to consist of a single semiconductor layer.

  Furthermore, the first GaN-based semiconductor region 17 is preferably adjacent to the light emitting layer that is the second GaN-based semiconductor region 19. By bringing the first GaN-based semiconductor region 17 and the second GaN-based semiconductor region 19 close to each other, there is an advantage that the first GaN-based semiconductor region 17 located far from the surface can be sufficiently excited.

(Example)
The growth process of the LED epitaxial layer structure will be described. A GaN substrate having a major mirror surface and a non-mirror rear surface is prepared. This GaN substrate was set in a metal organic chemical vapor deposition reactor. Ammonia (NH ₃ ) and hydrogen (H ₂ ) were supplied to the growth furnace and maintained for 10 minutes in an atmosphere of 1050 degrees Celsius for pretreatment (thermal cleaning). Thereafter, at 1150 degrees Celsius, a GaN film was grown on the main surface of the GaN substrate while adding Si. The GaN film thickness was 2 μm. Next, an In _0.05 Ga _0.95 N film was grown at a growth temperature of 800 degrees Celsius while adding Si as a layer for monitoring the state of the back surface of the GaN substrate. The thickness of the In _0.05 Ga _0.95 N film was 50 nm. Subsequently, an MQW light emitting layer was produced. The MQW light emitting layer includes undoped In _0.14 Ga _0.86 N well layers (thickness: 3 nm) and undoped In _0.01 Ga _0.99 N barrier layers (thickness: 15 nm) arranged alternately. Thereafter, a p-type Al _0.18 Ga _0.82 N electron blocking layer (thickness: 20 nm) is grown while adding Mg at a growth temperature of 1100 degrees Celsius, and a p-type GaN contact is added while adding Mg. A layer (thickness: 50 nm) was grown.

The LED epitaxial film structure (referred to as “LED structure A”) is shown.
Substrate 11: n-type GaN substrate buffer layer 21 having a non-specular back surface: Si-doped n-type GaN, 2 μm
First GaN-based layer 17: Si-doped n-type In _0.05 Ga _0.95 N, 50 nm
Second GaN-based layer 19: MQW light emitting layer Well layer: undoped In _0.14 Ga _0.86 N, 3 nm
Barrier layer: undoped In _0.01 Ga _0.99 N, 15 nm
Electron blocking layer 23: Mg-added p-type Al _0.18 Ga _0.82 N, 20 nm
Contact layer 25: Mg-added p-type GaN, 50 nm.
The band gap wavelength in this LED structure is GaN substrate: 365 nm
n-type In _0.05 Ga _0.95 N: 390 nm
Undoped In _0.14 Ga _0.86 N: 450 nm
It is.

  In order to obtain an LED structure in which fluctuations in crystal growth conditions are reflected, the LED structure B is manufactured using the same structure and growth sequence as the LED structure A, but with a growth run different from the LED structure A.

  FIG. 6 is a diagram showing the PL spectrum intensity of the LED structures A and B. 6A is a diagram showing a spectrum from the second GaN-based layer (light emitting layer) of the LED structures A and B, and FIG. 6B is a first GaN-based LED structure of the LED structures A and B. It is drawing which shows the spectrum from a layer (auxiliary layer). The peak of the PL spectrum near the wavelength of 450 nm is emitted from the MQW structure, and the peak of the PL spectrum near the wavelength of 390 nm is emitted from the auxiliary layer. For light emission from the MQW structure, the PL peak intensity ratio, ie (LED structure A) / (LED structure B) is 1.8. Regarding light emission from the auxiliary layer, the photoluminescence from the LED structure A is stronger than the photoluminescence from the LED structure B. This indicates that the roughness of the back surface of the substrate of the LED structure A is rough and there are many reflections from the back surface of the substrate.

A mirror surface was formed by polishing the back surfaces of the substrates of the LED structures A and B. Ni / Au was vapor-deposited as a p-side electrode, and Ti / Al was vapor-deposited as an n-side electrode to produce LED devices (referred to as “LED device A” and “LED device B”). The electroluminescence (EL) spectrum was measured by applying a current of 20 mA to the LED devices A and B. Light emission from the MQW structure was observed, and light emission from the auxiliary layer (In _0.05 Ga _0.95 N) was not observed. FIG. 7 is a diagram showing the EL spectral intensities of LED devices A and B. For light emission from the MQW structure, the EL peak intensity ratio, ie (LED device A) / (LED device B) is 1.3.

The measured values of PL spectrum intensity and EL spectrum intensity are shown below.
Device PL spectrum intensity EL spectrum intensity

MQW InGaN layer ratio MQW light emitting structure A: 6.32 × 10 ⁶ , 1.32 × 10 ⁶ , 47.9 1.27 × 10 ⁴
Structure B: 3.56 × 10 ⁶ , 1.00 × 10 ⁶ 35.6 9.77 × 10 ³
A / B: 1.78 times 1.34 times 1.30 times

  Examining the above values, the ratio (A / B) of EL spectral intensity is 1.30, while the ratio of PL spectral intensity (A / B) of MQW is about 1.8. That is, the quality of MQW cannot be accurately estimated using the PL spectrum intensity. On the other hand, the ratio of MQW to auxiliary layer (MQW / auxiliary layer) in the PL spectrum intensity is 1.34, which is close to the ratio (A / B) of EL spectrum intensity (A / B) of 1.30.

  The light extraction efficiency from the LED structure varies depending on the roughness of the back surface of the substrate. In this example, since the PL spectrum intensity from the auxiliary layer (InGaN layer) in the LED structure A is stronger than that in the LED structure B, it is estimated that the roughness of the back surface of the substrate of the LED structure A is large.

  When the ratio (MQW / auxiliary layer) is used to reduce the influence of the reflected light from the back surface of the substrate, the compensated PL spectrum intensity (1.34) becomes the EL spectrum intensity ratio (A / B) as described above. ) Approaching 1.30.

  For reasons such as material cost reduction, the back surface of the GaN substrate may be made non-mirrored (as sliced). The PL spectrum has a component that directly reaches the surface of the epitaxial substrate from the light emitting layer and a component that is reflected by the back surface of the substrate and reaches the surface of the epitaxial substrate, and is homoepitaxially grown on the GaN substrate as in this example. When there is a GaN layer, or when the refractive index difference between the GaN substrate and the epitaxial GaN-based layer is small, the reflection component from the back surface of the substrate cannot be ignored. The amount of reflected light from the back surface of the non-specular substrate is larger than that of the back surface that has been mirror-finished. It is because it becomes easy to come. Since the roughness of the back surface of the substrate varies independently of the variation of the crystal growth conditions, the reflection component has an influence on the change of the PL spectrum caused by the variation of the film forming conditions. In the observed PL spectrum, in addition to a signal indicating the quality of the light emitting layer, noise of a reflection component is included due to the back surface of the substrate. Therefore, it becomes difficult to evaluate the crystal quality using the PL spectrum.

In the embodiment of the present invention, the PL spectrum intensity from a semiconductor layer (auxiliary layer) having a band gap smaller than that of the substrate is measured. This semiconductor layer is preferably composed of a single film in which the PL spectrum intensity fluctuation for each film formation run is smaller than that of the light emitting layer. If the PL intensity of the semiconductor layer is used as an auxiliary, fluctuations in roughness on the back surface of the substrate can be monitored. For example, when the PL spectrum intensity is improved, it can be determined according to the following.
(A) If the PL spectrum intensity from the auxiliary layer was improved, the influence of the back surface increased.
(B) If the PL spectrum intensity from the auxiliary layer was not improved, the crystal quality of the light emitting layer was improved.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. In the present embodiment, for example, the present invention has described a semiconductor optical device having a quantum well structure in the present embodiment, but the present invention is not limited to the specific configuration disclosed in the present embodiment. In this embodiment, a semiconductor light emitting element such as a light emitting diode has been described. However, a semiconductor laser can also be used. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

FIG. 1 is a drawing showing a process flow of a method for producing a group III nitride semiconductor optical device and a method for measuring a photoluminescence spectrum according to an embodiment of the present invention. FIG. 2 is a schematic diagram schematically showing main steps of a method for producing a group III nitride semiconductor optical device and a method for measuring a photoluminescence spectrum. FIG. 3 is a schematic view schematically showing main steps of a method for producing a group III nitride semiconductor optical device and a method for measuring a photoluminescence spectrum. FIG. 4 is a schematic view schematically showing main steps of a method for producing a group III nitride semiconductor optical device and a method for measuring a photoluminescence spectrum. FIG. 5 shows an LED structure for reference that does not include the first GaN-based layer. FIG. 6 is a diagram showing the PL spectrum intensity of the LED structures A and B. FIG. 7 is a diagram showing the EL spectral intensities of the LED devices A and B.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Substrate, 11a ... Surface (main surface) of substrate 11, 11b ... Surface (back surface) of substrate 11, 11d ... Ground substrate, 13 ... Growth device, 15 ... Semiconductor stack, 17 ... First gallium nitride system Semiconductor region (first GaN-based semiconductor region), 19 ... second gallium nitride-based semiconductor region (second GaN-based semiconductor region), 21 ... buffer layer, 23 ... electron block layer, 25 ... contact layer, 27 ... Multiple quantum well structure, 27a ... well layer, 27b ... barrier layer, 27c ... barrier layer and / or guide layer, 31 ... PL measuring device,
33a, 33b ... electrodes, E1 ... substrate product, _LEX ... excitation light, _LOUT1 ... first component from the first GaN-based semiconductor region, _LOUT2 ... second from the second GaN-based semiconductor region Component, L (D) _OUT1 , L (D) _OUT2 ... Direct component, L (R) _OUT1 , L (R) _OUT2 ... Reflection component

Claims (10)

A method of fabricating a group III nitride semiconductor optical device,
Placing a semiconductor substrate having a major mirror surface and a non-mirror back surface in a growth apparatus;
A semiconductor stack including first and second gallium nitride based semiconductor regions is grown on the main surface of the semiconductor substrate with the growth apparatus to form a substrate product for the group III nitride semiconductor optical device. Process,
Irradiating the substrate product with excitation light and measuring a photoluminescence spectrum including a first component from the first gallium nitride based semiconductor region and a second component from the second gallium nitride based semiconductor region And a process of
Generating a ratio of the first component to the second component of the photoluminescence spectrum;
Comparing the predetermined value indicating the quality of the second gallium nitride based semiconductor region with the ratio, and sorting the substrate product based on the result of the comparison,
The first gallium nitride based semiconductor region is provided between the second gallium nitride based semiconductor region and the semiconductor substrate.   The method according to claim 1, wherein the second gallium nitride based semiconductor region has a multiple quantum well structure.   The method according to claim 2, wherein the first gallium nitride based semiconductor region comprises a single semiconductor layer. The peak wavelengths of the first and second components from the first and second gallium nitride based semiconductor regions are both larger than the band gap wavelength of the semiconductor substrate,
4. The method according to claim 1, wherein a peak wavelength of the second component is larger than a peak wavelength of the first component. 5.   The method according to claim 1, wherein the semiconductor substrate is a group III nitride substrate.   The method according to claim 1, further comprising forming an electrode for the group III nitride semiconductor optical device after the substrate product is selected. Method.   The method according to claim 1, wherein the second gallium nitride based semiconductor region includes a light emitting layer for the group III nitride semiconductor optical device.   The method according to claim 7, wherein the first gallium nitride based semiconductor region is adjacent to the light emitting layer.   9. The method according to claim 1, wherein the first gallium nitride based semiconductor region is made of InGaN, and the semiconductor substrate is made of GaN. A method for measuring a photoluminescence spectrum of a gallium nitride based semiconductor region,
Irradiating excitation light to the first and second gallium nitride based semiconductor regions grown on the main surface on a semiconductor substrate having a mirror main surface and a non-mirror back surface, the first and second Measuring photoluminescence spectra each including first and second components from a gallium nitride based semiconductor region;
Generating a ratio between the first component and the second component of the photoluminescence spectrum as a value indicating the quality of the second gallium nitride based semiconductor region,
The first gallium nitride based semiconductor region is provided between the second gallium nitride based semiconductor region and the semiconductor substrate.

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