JP2018206895A - ZnO-based semiconductor device and manufacturing method thereof - Google Patents

Abstract

A high-quality p-type ZnO-based semiconductor layer is realized. A manufacturing method of a ZnO-based semiconductor element includes: (a) an n-type doped with a non-doped ZnO-based material at a concentration of 5 × 10 16 cm −3 or more and 5 × 10 17 cm −3 or less on a ZnO-based semiconductor substrate. A step of epitaxially growing a ZnO-based semiconductor layer; and (b) a step of epitaxially growing a p-type ZnO-based semiconductor layer doped with Ag or at least one of group elements Ag and IIIb on the n-type ZnO-based semiconductor layer. And including. [Selection] Figure 3

Description

  The present invention relates to a ZnO-based semiconductor element and a method for manufacturing the same.

  Zinc oxide (ZnO) is a direct-transition semiconductor having a band gap energy of 3.37 eV at room temperature, and has a relatively high exciton binding energy of 60 meV. In addition, the raw materials are inexpensive and have a feature of little influence on the environment and the human body. For this reason, realization of a light-emitting element using ZnO with high efficiency, low power consumption and excellent environmental performance is expected.

  A ZnO-based semiconductor in which MgO or CdO is added to ZnO in order to adjust the band gap energy has physical properties similar to ZnO. A light-emitting device can be formed by epitaxially growing a ZnO-based semiconductor on a substrate. Epitaxial growth can be done by, but is not limited to, molecular beam epitaxy MBE.

  However, a ZnO-based semiconductor has a self-compensation effect due to strong ionicity, and it is difficult to control the p-type conductivity by crystal growth using a thermal equilibrium impurity doping technique such as a normal thermal diffusion technique. As acceptor impurities, VA (5A) group elements such as N, P, As and Sb, IA (1A) group elements such as Li, Na and K, and IB (1B) group elements such as Cu, Ag and Au are used. Research is underway to develop p-type ZnO-based semiconductors with practical performance. A technique for forming a p-type ZnO-based semiconductor layer by co-doping a p-type impurity and an n-type impurity has also been proposed. For example, a technique for obtaining a p-type layer by co-doping an acceptor such as Cu or Ag and a donor such as Ga on a ZnO-based semiconductor layer (for example, Patent Document 1) has been proposed.

Ag or the like that occupies the Zn site in the ZnO-based semiconductor serves as an acceptor that functions as a p-type impurity. For example, even if a ZnO-based layer co-doped with n-type impurity Ga and p-type impurity Ag is grown, it does not become p-type alone, but becomes p-type only after annealing. In order to make Ag function as a p-type impurity, it is considered necessary to first move Ag to Zn vacancies by thermal diffusion or the like. The inventors of the present application, for example, formed a ZnO-based semiconductor layer containing an n-type impurity Ga and a p-type impurity Ag, and formed the ZnO-based semiconductor layer in an environment where active oxygen is present and the pressure is less than 10 ⁻² Pa. A method of annealing to form a p-type has been proposed (for example, Patent Document 2).

  Ag has a large diameter in a ZnO-based semiconductor and is unlikely to move freely between lattices. The presence of lattice defects such as oxygen vacancies is desirable for the movement of Ag. If the ZnO-based crystal is annealed, it is considered that a situation in which Ag atoms can move can be realized by moving constituent atoms to generate lattice defects. When controlling the movement of Ag, the present inventors consider that an atmosphere in which active oxygen is present is preferable based on the results when a vacuum atmosphere in which oxygen does not exist is used.

  When Zn moves in the crystal, Zn vacancies and interstitial Zn are generated, and Ag can be trapped in the Zn vacancies. In order to make Ag a p-type impurity, Zn vacancies are necessary elements, and interstitial Zn is also generated with the generation of Zn vacancies. Interstitial Zn functions as a donor. When Zn moves, O which has lost its bonding partner also easily moves, and it is considered that oxygen vacancies are formed after O moves. Oxygen vacancies function as donors with low activation energy. The liberated oxygen moves between the lattices and evaporates to the outside when it reaches the surface. Formation of the p-type ZnO-based layer is accompanied by generation of crystal defects such as Zn vacancies, oxygen vacancies, interstitial Zn, and interstitial oxygen.

In addition, in a ZnO-based semiconductor light-emitting structure having a multiple quantum well light-emitting layer, there is also a proposal for improving light emission efficiency by causing energy transition through a donor level by doping a donor impurity in at least a part of the light-emitting layer. (For example, Patent Document 3). As an example, a multiple quantum well structure in which Ga is doped at a concentration of 1 × 10 ¹⁸ cm ⁻³ is disclosed.

JP 2004-221132 A, JP, 2015-159269, A Japanese Patent Application Laid-Open No. 2004-335792.

  The characteristics of the p-type ZnO-based semiconductor layer doped with acceptor impurities are not yet sufficiently high. It is desired to realize a high-quality p-type ZnO-based semiconductor layer.

According to one aspect of the embodiment,
A ZnO-based substrate;
An n-type ZnO-based semiconductor layer formed on a ZnO-based substrate and doped with Ga at a concentration of 5 × 10 ¹⁶ cm ⁻³ or more and 5 × 10 ¹⁷ cm ⁻³ or less;
a p-type ZnO-based semiconductor layer doped with at least one of Ag or Ag and a group IIIb element on the n-type ZnO-based semiconductor layer;
A ZnO-based semiconductor device having the following is provided.

According to another aspect of the embodiment,
(A) epitaxially growing an n-type ZnO-based semiconductor layer doped with Ga at a concentration of 5 × 10 ¹⁶ cm ⁻³ or more and 5 × 10 ¹⁷ cm ⁻³ or less on a ZnO-based semiconductor substrate;
(B) epitaxially growing a p-type ZnO-based semiconductor layer doped with Ag or at least one of group elements Ag and IIIb on the n-type ZnO-based semiconductor layer;
A method for manufacturing a ZnO-based semiconductor device including the present invention is provided.

1A is a schematic cross-sectional view showing an MBE apparatus, FIG. 1B is a schematic cross-sectional view of a sample in a prior study, and FIG. 1C is a schematic cross-sectional view showing a stacked structure in a p-type ZnO layer in the sample. It is. FIG. 2A is a graph showing a temperature profile of a sample preparation process in a comparative example, and FIG. 2B is a process diagram showing the contents of the process. FIG. 3A is a graph showing a temperature profile of a sample preparation process according to an embodiment, and FIG. 3B is a process diagram showing the contents of the process. FIG. 4A is a graph showing the SIMS measurement result for the sample of the comparative example, and FIG. 4B is a graph showing the SIMS measurement result for the sample of the example. 5A is a schematic diagram showing a Raman scattering measurement system, FIG. 5B is a graph showing Raman spectra for the samples of the comparative example and the example, and FIG. 5C is a ZnO crystal with respect to the peak intensity of the E ₂ ^high mode, which is the vibration mode of the ZnO crystal. is a graph showing the _a 1 (LO) mode ratio of the peak intensity of the _{[a 1 (LO)] /} [E 2 high] due to defects in the. In Comparative Examples and Examples, samples having different Ag concentrations in the p-type ZnO layer were prepared, and the ratio of the Raman scattering peak intensity to the change in Ag concentration based on the result of measuring Raman scattering [A ₁ (LO)] / it is a graph showing the _[E ^{2 high].} The ratio of the Raman scattering peak intensity to the Ag concentration based on the result of measuring Raman scattering in the samples of the comparative example and the example in which the p-type ZnO layer is co-doped with the p-type impurity Ag and the n-type impurity Ga [A ₁ (LO )] / [E ₂ ^high] . It is a graph which shows the photoluminescence spectrum of the undoped ZnO layer based on a comparative example, and the photoluminescence of the Ga dope ZnO layer based on an Example.

51 ZnO substrate, 52 ZnO buffer layer, 53 undoped ZnO layer,
54 alternately laminated structure, 71 vacuum chamber, 72 Zn source gun, 73 O source gun, 74 Mg source gun, 75 Ag source gun, 76 Ga source gun, 77 stage, 78 substrate, 79 film thickness meter, 80 RHEED gun, 81 screens,
S1-S6 Comparative Example Process, S11-S16 Example Process, 50 Samples,
91 excitation light, 92 scattered light, 93 detection optical system, 96 broad PL band,
97 Band gap emission, UD undoped, GaD Ga doped.

  The present inventors are studying the development of a high-quality p-type ZnO-based crystal. As described above, the formation of the p-type ZnO-based layer involves generation of crystal defects such as Zn vacancies, oxygen vacancies, interstitial Zn, and interstitial oxygen. If the number of defects in the p-type layer increases, the number of n-type traps also increases, preventing improvement in crystallinity. The presence or absence of defects becomes a problem when producing highly efficient light emitting diodes (LEDs).

  When researching an LED in which a p-type ZnO-based crystal layer doped with Ag as a p-type impurity is formed on an n-type ZnO-based crystal layer, a non-doped n-type ZnO-based crystal layer is used according to a conventional example (comparison) It has been found that different results are obtained between the example) and when the n-type ZnO-based crystal layer is doped with a small amount of Ga. The growth of the ZnO-based semiconductor layer was performed by molecular beam epitaxy (MBE).

FIG. 1A is a schematic cross-sectional view showing an MBE apparatus. In the vacuum chamber 71, a Zn source gun 72, an O source gun 73, an Mg source gun 74, an Ag source gun 75, and a Ga source gun 76 are provided. The back pressure during operation of the MBE apparatus is 10 ⁻⁸ Pa to 10 ⁻² Pa.

  The Zn source gun 72, the Mg source gun 74, the Ag source gun 75, and the Ga source gun 76 are Knudsen cells that contain solid sources of Zn (7N), Mg (6N), Ag (6N), and Ga (7N), respectively. A Zn beam, Mg beam, Ag beam, and Ga beam are emitted by heating the cell.

The O source gun 73 includes, for example, an electrodeless discharge tube using a radio frequency of 13.56 MHz. The O source gun 73 converts O ₂ gas (6N) into plasma in the electrodeless discharge tube and emits an O radical (O ^* ) beam. As the discharge tube material, alumina or high purity quartz can be used.

  A stage 77 having a substrate heater holds the substrate 78. Each of the source guns 72 to 76 includes a cell shutter. By opening and closing each cell shutter, it is possible to switch between a state where each beam is directly irradiated onto the substrate 78 and a state where each beam is not directly irradiated. A shutter is also provided in front of the substrate 78. By irradiating a desired beam on the substrate 78 at a desired timing, a ZnO-based compound semiconductor layer having a desired composition can be grown.

  A film thickness meter 79 for measuring the thickness of the film deposited on the substrate is disposed on the side of the stage 77. A RHEED gun 80 that emits an electron beam and a screen 81 that receives and images the electron beam reflected by the substrate 78 are disposed opposite to each other with the stage 77 interposed therebetween.

  With reference to FIG. 1B, a basic configuration of a ZnO-based semiconductor light-emitting diode having a homojunction in the prior study will be described. Using the MBE apparatus shown in FIG. 1A, a ZnO buffer layer 52, an n-type ZnO layer 53, and a p-type ZnO layer 54 are formed by MBE on a Zn-faced ZnO (0001) substrate 51 having n-type conductivity.

FIG. 1C is a partially enlarged cross-sectional view illustrating a configuration example of the p-type ZnO layer 54. Undoped ZnO layers 54a and AgO layers 54b are alternately stacked to form, for example, 30 pairs of alternately stacked layers to form p-type ZnO layers. “AgO” represents a silver oxide that can be expressed as AgO _x , such as AgO (silver oxide (II)) or Ag ₂ O (silver oxide (I)). A co-doped p-type ZnO layer can be formed by using a Ga-doped ZnO layer instead of the undoped ZnO layer and alternately forming the AgO layer.

  Hereinafter, a comparative example and an Example are demonstrated more concretely. As shown in FIG. 1B, the sample has a configuration in which a ZnO buffer layer 52 is formed on a ZnO substrate 51, an n-type ZnO layer 53 is formed thereon, and a p-type ZnO layer is formed thereon. . FIG. 2 shows a comparative example, and FIG. 3 shows an example. 2A and 3A are graphs showing temperature changes with time and implementation steps, and FIGS. 2B and 3B are process diagrams showing sample configurations and the contents of each step for forming these configurations.

With reference to FIG. 2, preparation of a sample of a comparative example will be described. As shown in the temperature profile graph of FIG. 2A, the ZnO substrate 51 is heated to 850 ° C., and thermal cleaning is performed at 850 ° C. for about 30 minutes as step S1. Subsequently, the temperature is lowered to 220 ° C., and as a step S2, a molecular beam as a raw material is supplied at 220 ° C. for 5 minutes to grow a ZnO buffer layer (low temperature growth buffer layer) 52. Zn flux F _Zn was 1.4 A / sec, the O ₂ flow rate was 1 sccm, and the RF power was 150 W.

  Subsequent to step S2, the substrate temperature is raised to 850 ° C., and annealing is performed at 850 ° C. for 30 minutes as step S3. The crystallinity of the low temperature growth buffer layer was improved, and a buffer layer 52 having a thickness of about 30 nm was obtained. Subsequent to the annealing in step S3, the substrate temperature is raised to 920 ° C., and in step S4, an undoped ZnO layer having a thickness of about 700 nm is grown. The undoped ZnO layer becomes the n-type ZnO layer 53.

Subsequent to step S4, the substrate temperature is lowered to 220 ° C., and in step S5, a stacked structure in which a p-type ZnO layer 54 having a thickness of about 270 nm is formed on the n-type ZnO layer 53 is grown. As shown in FIG. 2B, after the undoped ZnO layer was grown six times, the unit set for growing the AgO layer once was repeated 90 times. An oxygen radical O ^* irradiation process is inserted between each growth process. The O ^* irradiation process was performed for 3 seconds, the undoped ZnO layer was grown for 3 seconds, and the AgO layer was grown for 13 seconds. A laminated structure having a thickness of about 270 nm was formed. The VI / II flux ratio was 0.92, and the temperature of the Ag source was 875 ° C. As will be described later, a Ga-doped ZnO layer may be grown instead of the undoped ZnO layer. After the growth of the laminated structure of S5, the substrate temperature is raised to 720 ° C., and in step S6, activation is performed in the MBE chamber 71 in an atmosphere with a back pressure of less than 10 ⁻² Pa at a temperature of 720 ° C. for 20 minutes. Annealing was performed under intermittent irradiation of an oxygen radical O ^* beam. In the period without oxygen radical irradiation, movement of Ag may occur together with generation and movement of oxygen vacancies. Oxygen vacancies may be suppressed and eliminated during the period with oxygen radical irradiation. As a result, a high acceptor concentration is expected.

With reference to FIG. 3, the sample preparation of the embodiment will be described. As shown in the temperature profile graph of FIG. 3A, the ZnO substrate 51 is heated to 850 ° C., and thermal cleaning is performed at 850 ° C. for about 30 minutes as step S11. Subsequently, the temperature is lowered to 220 ° C., and as a step S12, a source molecular beam is supplied at 220 ° C. for 5 minutes to grow a ZnO buffer layer (low temperature growth buffer layer) 52. Zn flux F _Zn was 1.4 A / sec, the O ₂ flow rate was 1 sccm, and the RF power was 150 W.

  Subsequent to step S12, the substrate temperature is raised to 850 ° C., and annealing is performed at 850 ° C. for 30 minutes as step S13. The crystallinity of the low temperature growth buffer layer was improved, and a buffer layer 52 having a thickness of about 30 nm was obtained. Subsequent to the annealing in step S13, the substrate temperature is raised to 920 ° C., and in step S14, a Ga-doped ZnO layer having a thickness of about 700 nm is grown. In addition, although an undoped ZnO layer to be an n-type ZnO layer is doped with Ga serving as an n-type impurity, the amount thereof is very small and is not so large as to impart n-type conductivity by Ga doping.

Subsequent to step S14, the substrate temperature is lowered to 220 ° C., and in step S15, a stacked structure in which a p-type ZnO layer 54 having a thickness of about 270 nm is formed on the n-type ZnO layer 53 is grown. As shown in FIG. 3B, after the undoped ZnO layer was grown six times, the unit set for growing the AgO layer once was repeated 90 times. An oxygen radical O ^* irradiation process is inserted between each growth process. The O ^* irradiation process was performed for 3 seconds, the undoped ZnO layer was grown for 3 seconds, and the AgO layer was grown for 13 seconds. A laminated structure having a thickness of about 270 nm was formed. The VI / II flux ratio was 0.92, and the temperature of the Ag source was 875 ° C. As will be described later, a Ga-doped ZnO layer may be grown instead of the undoped ZnO layer. After the growth of the laminated structure of S15, the substrate temperature is raised to 720 ° C., and in step S16, activation is performed in the MBE chamber 71 in an atmosphere with a back pressure of less than 10 ⁻² Pa at a temperature of 720 ° C. for 20 minutes. Annealing was performed under intermittent irradiation of an oxygen radical O ^* beam. In the period without oxygen radical irradiation, movement of Ag may occur together with generation and movement of oxygen vacancies. Oxygen vacancies may be suppressed and eliminated during the period with oxygen radical irradiation. As a result, a high acceptor concentration is expected.

  The difference between the sample of the example and the sample of the comparative example is that the n-type ZnO layer of the comparative example is non-doped, whereas the n-type ZnO layer of the example is Ga-doped.

FIG. 4 shows the result of secondary ion mass spectrometry (SIMS) measurement. The graph of FIG. 4A shows the result of SIMS measurement for the comparative example, and the graph of FIG. 4B shows the result of SIMS measurement for the sample of the example. In the graph, the horizontal axis indicates the depth from the surface of the sample in units (nm), and the vertical axis indicates the concentration of Ag and Ga detected by SIMS in units (cm ⁻³ ). In both samples, Ag, which is a p-type impurity, is detected from the surface to a depth of about 270 nm. The depth of the p-type ZnO layer is about 270 nm. 3.0 × 10 ²⁰ cm ⁻³ is detected as the silver concentration [Ag] in the sample of the comparative example, and 2.8 × 10 ²⁰ cm ⁻³ is detected as the silver concentration [Ag] in the sample of the example. An n-type ZnO layer exists below the p-type ZnO layer.

As shown in FIG. 4A, in the measurement result of the comparative example, the Ga concentration is below the lower detection limit in the entire thickness range. As shown in FIG. 4B, in the sample of the example, the Ga concentration in the p-type ZnO layer is about zero, but in the n-type ZnO layer below it, the Ga concentration is about 1 × 10 ¹⁷ cm ^−3. It is. Ga is not detected in the n-type ZnO layer of the comparative example, but Ga of 1 × 10 ¹⁷ cm ⁻³ is detected in the n-type ZnO layer of the example. The concentration of 1 × 10 ¹⁷ cm ⁻³ is weak as the concentration of the conductivity-type imparting impurity. The crystal component is also in the order of ppm.

  FIG. 5 shows an experiment in which Raman scattering measurement was performed on the samples of the comparative example and the example. FIG. 5A is a side view showing an outline of Raman scattering. The excitation light 91 of the laser beam was irradiated on the p-type ZnO layer surface side of the sample 50, and the scattered light 92 from the p-type ZnO layer surface side was detected by the detection optical system. The detection optical system includes a spectroscopic mechanism, detects scattered light that is Raman-shifted from the wavelength of the excitation light, and can detect a Raman scattered light peak as a function of the Raman shift. Since the reflected scattered light is measured, it is considered that the scattered light from the p-type ZnO layer appears most strongly.

FIG. 5B is a graph showing a Raman scattering spectrum detected as a function of Raman shift. The horizontal axis indicates the Raman shift in units (cm ⁻¹ , Kaiser), and the vertical axis indicates the detected intensity of the Raman scattered light in units (count). The spectrum Em obtained from the sample of the example and the spectrum Cf obtained from the sample of the comparative example are written in parallel by shifting the vertical axis position. The peak of the E ₂ ^high mode, which is the original vibration mode of the ZnO crystal, is clearer in Example Em than in Comparative Example Cf, suggesting that the crystallinity of the ZnO crystal has been improved. The peak intensity of the A ₁ (LO) mode, which is said to be a vibration mode caused by oxygen vacancies or interstitial Zn, is smaller in Example Em than in Comparative Example Cf. The sample of the example suggests that the lattice defects are reduced.

FIG. 5C shows the ratio of the scattering peak A ₁ (LO) due to lattice defects to the original scattering peak E ₂ ^high of ZnO crystal, [A ₁ (LO)] / [E ₂ ^high ] as a function of Ag concentration. It is a graph. The horizontal axis indicates the Ag concentration in units (cm ⁻³ ), and the vertical axis indicates the Raman scattering peak ratio [A ₁ (LO)] / [E ₂ ^high ]. The ratio, which was about 0.6 in the comparative example, is reduced to about 0.15 in the example. A clear crystallinity improvement is suggested. In FIG. 5, the Ag concentration of the p-type ZnO layer is only one in both the comparative example and the example.

FIG. 6 is a graph showing the results of Raman measurement after forming a plurality of samples having different Ag concentrations in the p-type ZnO layer. The horizontal axis indicates the Ag concentration of the p-type ZnO layer in units (cm ⁻³ ), and the vertical axis indicates the Raman scattering peak ratio [A ₁ (LO)] / [E ₂ ^high ]. Although it cannot be said that the number of samples is sufficiently large, the [A ₁ (LO)] / [E ₂ ^high ] ratio of the comparative example is approximated to y = 3E-21x−0.2747, and the [A ₁ (LO )] / [E ₂ ^high ] ratio is approximated as y = 3E-21x-0.5613, the crystallinity of the p-type ZnO crystal layer is greatly improved in the sample of the example compared to the sample of the comparative example. It is suggested that It is considered that the crystallinity of the p-type ZnO layer grown thereon was significantly improved by doping Ga into the n-type ZnO layer at 1 × 10 ¹⁷ cm ⁻³ . The sample p-type ZnO layer described above was doped only with Ag as a p-type impurity. A p-type ZnO layer can also be formed by co-doping n-type impurity Ga together with p-type impurity Ag.

FIG. 7 is a graph showing a Raman scattering result of a sample in which a p-type ZnO layer is co-doped with p-type impurity Ag and n-type impurity Ga. In the comparative example, the n-type ZnO layer that is the base of the p-type ZnO layer is undoped ZnO, and in the example, the n-type ZnO layer that is the base of the p-type ZnO layer is Ga-doped in the same manner as the above-described sample. is there. The horizontal axis in FIG. 7 indicates the Ag concentration in units (cm ⁻³ ), and the vertical axis indicates the Raman scattering peak intensity ratio [A ₁ (LO)] / [E ₂ ^high ]. When the measurement plot of the comparative sample is approximated as y = 7E-22x + 0.1933 and the plot of the example sample is approximated as y = 7E-22x-0.0618, the Raman scattering in the sample of the example compared to the comparative example The peak intensity ratio [A ₁ (LO)] / [E ₂ ^high ] is clearly reduced, suggesting that the crystallinity of the p-type ZnO layer is improved. It is considered that the crystallinity of the p-type ZnO layer is improved when the n-type ZnO layer serving as the base of the p-type ZnO layer is doped with a small amount of Ga, although the causal relationship is unknown.

FIG. 8 is a graph showing photoluminescence spectra obtained from the undoped n-type ZnO layer and the Ga-doped n-type ZnO layer when the undoped n-type ZnO layer and the Ga-doped n-type ZnO layer are irradiated with excitation light. The photoluminescence UD from the undoped ZnO layer emits a broad band emission 96 over a wide wavelength region from 430 nm to 630 nm longer than the band gap wavelength. In photoluminescence GaD from a Ga-doped ZnO layer, no broad band emission 96 occurred when Ga was doped to some extent. In the Ga concentration range from 5 × 10 ¹⁶ cm ⁻³ to 5 × 10 ¹⁷ cm ^−3, no broad band emission occurred, and the mobility increased with increasing Ga concentration. This is a unique phenomenon in which the mobility is improved by the addition of impurities. When the Ga concentration of 5 × 10 ¹⁷ cm ⁻³ was exceeded, especially when the concentration of 10 ¹⁸ cm ⁻³ was exceeded, the crystallinity gradually deteriorated.

The Ga concentration range from 5 × 10 ¹⁶ cm ⁻³ to 5 × 10 ¹⁷ cm ⁻³ coincides with the Ga concentration of 1 × 10 ¹⁷ cm ⁻³ doped in the n-type ZnO layer of the example sample shown in FIG. Doping 5 × 10 ¹⁶ cm ^{−3 to} 5 × 10 ¹⁷ cm ⁻³ of Ga into the n-type ZnO layer that is the base of the p-type ZnO layer improves the crystallinity of the p-type ZnO layer, and thus a high-quality light-emitting diode Is expected to be feasible.

  Although the experimental results using ZnO crystals have been described above, similar results are expected if the stacked structure is an n-type underlayer that forms a homo bond with a ZnO-based semiconductor material and a p-type layer formed thereon. Let's be done. In the case of a homojunction that forms a pn junction in the same material, it is considered that the crystallinity of the underlayer strongly affects the crystallinity of the crystal layer grown thereon.

  In the active layer having a quantum well structure, a well layer and a barrier layer of different materials are stacked, so that a boundary between different materials is formed in the active layer. When the active layer is formed on the underlayer, the crystallinity effect of the underlayer is considered to be greatly limited at the dissimilar material boundary in the active layer, and the crystallographic effect is completely different from that of the homojunction. Become.

  As mentioned above, although this invention was demonstrated along contrast with a comparative example and an Example, the illustrated material, a numerical value, a process, etc. are illustrations and are not restrictive. It will be apparent to those skilled in the art that various modifications, substitutions, improvements, and the like can be made.

Claims (5)

A ZnO-based semiconductor substrate;
An n-type ZnO based semiconductor layer formed on the ZnO based semiconductor substrate and doped with Ga at a concentration of 5 × 10 ¹⁶ cm ⁻³ or more and 5 × 10 ¹⁷ cm ⁻³ or less on a non-doped ZnO based semiconductor;
A p-type ZnO-based semiconductor layer formed on the n-type ZnO-based semiconductor layer and doped with Ag or at least one of Ag and a group IIIb element;
ZnO-based semiconductor element having   The ZnO-based semiconductor element according to claim 1, wherein the ZnO-based semiconductor is ZnO, and at least one of the group IIIb elements is Ga. (A) a step of epitaxially growing an n-type ZnO based semiconductor layer doped with a non-doped ZnO based material at a concentration of 5 × 10 ¹⁶ cm ⁻³ or more and 5 × 10 ¹⁷ cm ⁻³ or less on a ZnO based semiconductor substrate; ,
(B) epitaxially growing a p-type ZnO-based semiconductor layer doped with Ag or at least one of group elements Ag and IIIb on the n-type ZnO-based semiconductor layer;
For producing a ZnO-based semiconductor device containing further,
(C) annealing the structure in which the p-type ZnO-based semiconductor layer is grown in an environment where active oxygen is present and the pressure is less than 10 ⁻² Pa;
The manufacturing method of the ZnO type | system | group semiconductor element of Claim 3 containing this.   The method for manufacturing a ZnO-based semiconductor element according to claim 3 or 4, wherein the ZnO-based semiconductor is ZnO, and at least one of the group IIIb elements is Ga.

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