JP2015137189A - Ag-doped p-type ZnO-based semiconductor crystal layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Ag-doped low-resistance p-type ZnO-based semiconductor crystalline layer.SOLUTION: There is provided an Ag-doped p-type ZnO-based semiconductor crystalline layer doped with Ag having an atomic ratio of positive elements of 2% or higher below 3%.

Description

  The present invention relates to an Ag-doped p-type ZnO-based semiconductor crystal layer. A II-VI group semiconductor containing Zn as the IIB group element and O as the VIB group element is called a ZnO-based semiconductor. The amount of Ag doping is expressed as the atomic ratio (%) of the positive element.

  In addition, the positive element in this application is a + II element such as Zn and Mg in a ZnO-based semiconductor crystal, and the atomic ratio of the positive element is a ratio to the concentration of all the positive elements in the ZnO-based semiconductor crystal. Point to. That is, the atomic ratio of the positive element of Ag is a value obtained by dividing the concentration of Ag atoms contained in the ZnO-based semiconductor crystal by the concentration of all positive elements in the ZnO-based semiconductor crystal.

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

  The n-type conductivity of the ZnO-based semiconductor can be obtained without doping impurities. By doping with a donor impurity such as Ga, n-type conductivity can be increased. Since the ZnO-based oxide semiconductor has a self-compensation effect due to strong ionicity, it is difficult to control the p-type conductivity by a crystal growth method using a thermal equilibrium impurity doping method such as a normal thermal diffusion method. Therefore, in order to obtain a p-type ZnO-based oxide semiconductor having practical performance, molecular beam epitaxy (MBE), laser molecular beam epitaxy, metal organic chemical vapor deposition (MOCVD), remote plasma MOCVD, sputtering, etc. Development of p-type ZnO-based semiconductor layers has been promoted by various non-thermal equilibrium growth methods.

  To date, group VA elements such as N, P, As, and Sb, group IA elements such as Li, Na, and K, and group IB elements such as Cu, Ag, and Au have been studied as acceptor impurities. The carrier concentration is still low, and sufficient quality including reproducibility and stability has not been obtained. Techniques such as co-doping of two types of impurities have been considered. A technique for obtaining a p-type layer by co-doping an acceptor such as Cu or Ag with a donor such as Ga (see, for example, Patent Document 1), or a technique for obtaining a p-type layer by co-doping nitrogen and a group IB element (for example, Patent Document 2) has been proposed. In addition, a technique of doping an acceptor such as N or Cu into at least one of superlattice layers having a stacked structure of MgZnO layers and ZnO layers (for example, see Patent Document 3) has been proposed.

JP 2004-221132 A JP 2009-256142 A JP 2009-21540 A

  An object of the present invention is to provide a low-resistance p-type ZnO-based semiconductor crystal layer doped with Ag.

  According to one aspect of the present invention, there is provided an Ag-doped p-type ZnO-based semiconductor crystal layer doped with 2% or more and less than 3% of Ag in terms of a positive element.

  According to another aspect of the present invention, a Ag-doped p-type ZnO-based semiconductor crystal layer, wherein an Ag interatomic distance is greater than 6.169Å and 10.045Å or less. A p-type ZnO-based semiconductor crystal layer is provided.

  According to the present invention, a low-resistance p-type ZnO-based semiconductor crystal layer doped with Ag can be provided.

FIG. 1 is a schematic cross-sectional view showing an example of an MBE apparatus. FIG. 2 is a conceptual diagram showing the relationship between the orbital level, the hybrid polarity energy Δ between MO, and the hybrid shared energy V. FIG. 3A is a band diagram when Ag or Cu is doped into ZnO among the transition metals, and FIG. 3B is a hybrid polar energy Δ, Ag or Cu when Ag or Cu is doped into ZnO. 3 is a table comparing the interatomic distance d with O and the value of 1 / d ² . FIG. 4 is a conceptual diagram illustrating a spatial distance between electrons due to a difference in M-O anti-bonding orbital bandwidth. FIG. 5 is a table showing theoretical calculation results by the present inventors. Figure 6 is a conceptual diagram showing changes in the width and _{E F} of M-O anti-bonding orbital bands for doping concentration. FIG. 7 is a diagram showing a model of an Ag-doped ZnO semiconductor crystal when the Ag concentration is 1 at%. FIG. 8 is a diagram showing a model of an Ag-doped ZnO semiconductor crystal when the Ag concentration is 2 at%. FIG. 9 is a diagram showing a model of an Ag-doped ZnO semiconductor crystal when the Ag concentration is 3 at%. FIG. 10 is a schematic cross-sectional view for explaining a method for manufacturing an Ag-doped p-type ZnO-based semiconductor crystal layer according to an example. FIG. 11 is a schematic cross-sectional view of a ZnO based semiconductor light emitting device.

  First, a crystal manufacturing apparatus used for growing a ZnO-based semiconductor layer or the like will be described. In the embodiment, a molecular beam epitaxy (MBE) method is used as a crystal manufacturing method.

  FIG. 1 is a schematic cross-sectional view showing an example of an MBE apparatus. In the vacuum chamber 101, a Zn source gun 102, an O source gun 103, an Mg source gun 104, an Ag source gun 105, and another solid source gun 106 are provided.

Zn source gun 102, Mg source gun 104, Ag source gun 105, and other solid source gun 106 contain Zn (7N), Mg (6N), Ag (6N), and other solid solid sources, respectively. A Zn beam, an Mg beam, an Ag beam, and other molecular beams (for example, a Ga beam) can be emitted by heating the cell. The O source gun 103 includes an electrodeless discharge tube using a radio frequency (for example, 13.56 MHz), converts O ₂ gas (6N) into plasma, and emits an O radical beam. As the discharge tube material, alumina, high-purity quartz, boron nitride or the like can be used.

  A stage 107 including a substrate heater is disposed in the vacuum chamber 101 and holds the growth substrate 108. Each of the source guns 102 to 106 includes a cell shutter, and switches between a state of irradiating a beam on the growth substrate 108 and a state of not irradiating the growth substrate 108 by opening and closing the cell shutter. A ZnO-based compound semiconductor layer having a desired composition can be grown on the growth substrate 108 by supplying a desired beam at a desired timing.

By adding Mg to ZnO to form a Mg _x Zn _1-x O mixed crystal, the band gap can be expanded according to the Mg composition x. Since ZnO has a wurtzite structure (hexagonal crystal) and MgO has a rock salt structure (cubic crystal), the Mg composition x is limited. When maintaining the wurtzite structure, Mg _x Zn _1-x O (0 ≦ x ≦ 0.6) is set.

A film thickness meter 109 using a crystal resonator is provided in the vacuum chamber 101. From deposition rate measured by a film thickness meter 109, flux strength, such as Zn beam from a solid source (e.g. expressed as F _Zn) is obtained.

  A gun 110 for reflection high-energy electron diffraction (RHEED) and a screen 111 for projecting a RHEED image are attached to the vacuum chamber 101. From the RHEED image, the surface flatness and growth mode of the crystal layer formed on the substrate 108 can be evaluated.

  When the crystal is grown two-dimensionally and the surface is epitaxially grown (single crystal growth), the RHEED image shows a streak pattern. In the case of epitaxial growth (single crystal growth) where the crystal grows three-dimensionally and the surface is not flat, the RHEED image shows a spot pattern. In the case of polycrystalline growth, the RHEED image is a ring pattern. Therefore, from the RHEED image, it is possible to know whether the surface is flat or not flat when the growth layer is single crystal or polycrystal.

Next, the VI / II flux ratio will be described. The flux intensity of Zn beam expressed as _{J Zn,} the flux intensity of the Mg beam expressed as _{J Mg,} representing the flux intensity of O radical beam and _{J O.} The beam of Zn or Mg, which is a group II material, contains Zn or Mg of atoms or clusters containing a plurality of atoms, and both atoms and clusters are effective for crystal growth. The O beam, which is a gas material, contains atomic radicals and neutral molecules. Here, the flux intensity of atomic radicals effective for crystal growth is considered.

The adhesion coefficient indicating the ease of adhesion of Zn to the crystal is denoted by k _Zn , the adhesion coefficient indicating the ease of adhesion of Mg is denoted by k _Mg, and the adhesion coefficient indicating the ease of adhesion of O is denoted by k 2 _O. Zn adhesion coefficient k _Zn and flux strength J _Zn product k _Zn J _Zn , Mg adhesion coefficient k _Mg and flux strength J _Mg product k _Mg J _Mg , and O adhesion coefficient k _O and flux strength J product k _O J _O of _O, respectively, Zn atoms adhering per unit time per unit area of the substrate, corresponding to the Mg atom, and the number of O atoms.

k _Zn J _Zn and _k Mg to the sum of _{J Mg} is the ratio of _{k O J O k O J O} / a _{(k Zn J Zn + k Mg} J Mg), defined as VI / II flux ratio. A case where the VI / II flux ratio is smaller than 1 is referred to as a group II rich condition (or a Zn rich condition when Mg is not included), and a case where the VI / II flux ratio is equal to 1 is referred to as a stoichiometric condition. A case where the II flux ratio is larger than 1 is called a VI group rich condition (or an O rich condition). In the crystal growth on the + c plane (Zn plane), if the substrate surface temperature is 850 ° C. or lower, the adhesion coefficients k _Zn , k _Mg , and k 2 _O can be regarded as 1, and the VI / II flux ratio is It can be expressed as J _O / (J _Zn + J _Mg ).

Specifically, the VI / II flux ratio can be calculated by the following procedure, for example. Take ZnO growth as an example. The Zn flux is measured as a _Zn deposition rate F _Zn (nm / s) at room temperature by a film thickness monitor using a crystal resonator. The unit of Zn flux is converted from F _Zn (nm / s) to J _Zn (atoms / cm ² s). O radical flux is calculated | required as follows. Under constant O radical beam irradiation conditions (for example, O ₂ flow rate 2.0 sccm / RF power 300 W), Zn flux is changed to grow ZnO, and the Zn flux dependence of the ZnO growth rate is experimentally determined. By fitting the result using an approximate expression of ZnO growth rate G _ZnO : G _ZnO = [(k _Zn J _Zn ) ^-1 + (k _O J _O ) ^-1 ] ^-1 , radical flux _{J O} is calculated. Thus from Zn flux _{J Zn} and O radical flux _{J O} obtained, it is possible to calculate the VI / II flux ratio.

  The present inventors have studied a method for obtaining low-resistance p-type conductivity by using Ag as a single acceptor impurity.

  In general, when two atoms form a chemical bond, the outermost electrons of the two atoms are divided into an electron that contributes only to the chemical bond and an electron that does not contribute to the chemical bond. Each electronic state (both spatial distribution and corresponding energy distribution) is called a bonding state and an anti-bonding state.

  In order to obtain a low-resistance p-type ZnO-based semiconductor thin film by doping the transition metal M, M-O anti-bonding orbital energy (anti-bonding orbital level) derived from the chemical bond between the transition metal M and oxygen O ), That is, the orbital level (activation energy) from the top of the valence band must be lowered. The transition metal M includes copper (Cu), silver (Ag), and gold (Au).

  FIG. 2 shows orbital levels (O hybrid orbitals in O (hereinafter referred to as O hybrid energy levels) in M and M orbitals in M (hereinafter referred to as Md level energies). ) And the hybrid polarity energy Δ and the hybrid shared energy V between M and O are conceptually shown.

As can be seen from FIG. 2, in order to lower the orbital level, the following control (1) and (2) of the hybrid polarity energy Δ between MO and the hybrid shared energy V is required.
(1) Lower the hybrid polarity energy Δ (the energy difference between the O hybrid energy level and the Md level).
(2) Decrease the hybrid shared energy V (a value inversely proportional to the square of the interatomic distance between M and O).

FIG. 3A is a band diagram when Ag or Cu is doped into ZnO among the transition metals, and FIG. 3B is a hybrid polar energy Δ, Ag or Cu when Ag or Cu is doped into ZnO. 3 is a table comparing the interatomic distance d with O and the value of 1 / d ² .

Ag and Cu substitute Zn at the Zn position in ZnO. In the case of Ag, the hybrid polar energy Δ is 0.665 eV, and the interatomic distance d with O is 2.20 Å. 1 / d ² is 0.207Å− ² . In the case of Cu, the hybrid polar energy Δ is 1.13 eV, and the inter-atomic distance d with O is 1.98 Å. 1 / d ² is 0.255Å− ² .

Ag is compared with Cu, which is a transition metal of the same group (Group IB),
(1) Hybrid polarity energy Δ (energy difference between O hybrid orbital level and Md orbital level) is small,
(2) The hybrid shared energy V (value inversely proportional to the square of the interatomic distance between M and O) is small.
It can be seen that it has the characteristics.

  Actually, for example, when calculation is performed within a general semiconductor doping concentration range (for example, 1 at%), the activation energy is 386 meV for Ag and 700 meV for Cu. Thus, it can be said that Ag is a dopant which is superior to, for example, reducing the resistance p-type of ZnO-based semiconductors compared to Cu.

  On the other hand, even if the activation energy is small, if the width of the M-O anti-bonding orbital band is small, the excited excited electrons from the valence band and the occupied electrons of the orbit where the excited electrons enter Spatial distance between and is shortened.

  FIG. 4 conceptually shows the spatial distance between electrons due to the difference in the M-O anti-bonding orbital bandwidth.

  When the band width is narrow, the Coulomb repulsive force between electrons in the M-O anti-bonding orbital band becomes strong, so that the possibility of occupying the excited electrons from the valence band is suppressed. As a result, holes (holes) are hardly generated at the top of the valence band, and it is difficult to reduce the resistance to p-type.

  The present inventors have found by theoretical calculation that, for example, the width of the M-O anti-bonding orbital band changes depending on the doping concentration in the case of Ag.

  FIG. 5 is a table showing theoretical calculation results by the present inventors. The table shows the Ag-O anti-bonding orbital band width and the Ag doping concentration dependence of Ag-O anti-bonding orbital energy (activation energy).

  The band width was calculated to be 58 meV for an Ag concentration range of 1 at% or less, 98 meV for an Ag concentration of 2 at%, and 245 meV for an Ag concentration of 3 at%.

  The activation energy was calculated to be 386 meV at an Ag concentration range of 1 at% or less, 348 meV at an Ag concentration of 2 at%, and 456 meV at an Ag concentration of 3 at%. It is confirmed that the activation energy basically increases as the doping concentration increases. An increase in activation energy makes it difficult to excite electrons from the valence band, that is, it makes it difficult to generate hole carriers. Therefore, it becomes an inhibitor of the low resistance p-type ZnO-based semiconductor.

Figure 6 is a conceptual diagram showing changes in the width and _{E F} of M-O anti-bonding orbital bands for doping concentration.

For example, the doping concentration of the transition metal M is Ag is increased, the interaction between the Ag and Ag is increased (strongly coupled state), E _F rises accompanied by bandwidth increase.

  The considerations by the present inventors will be described with reference to FIGS. 5 and 7 to 9.

When the static dielectric constant is 8.49 and the effective mass of holes is 0.45 to 0.59, the Bohr radius (Bohr radius (hole)) for holes is
7.64Å <Bohr radius (hole) <10.17Å
It is estimated.

  For example, when the interatomic distance (Ag-Ag interatomic distance) of Ag doped in the ZnO-based semiconductor crystal is shorter than the Bohr radius (a value included in the range of 7.64 to 10.17 cm), Ag and The interaction with Ag increases (strongly coupled state), and the MO antibonding orbital level (activation energy), that is, the acceptor excitation level increases, making it difficult to obtain p-type carriers. become.

  FIG. 7 shows a model of an Ag-doped ZnO semiconductor crystal when the Ag concentration is 1 at%.

In the range where the Ag concentration is 1 at% or less corresponding to a general semiconductor doping range (about 1 × 10 ¹⁷ cm ^{−3 to} 5 × 10 ²⁰ cm ⁻³ ), the distance between Ag and Ag atoms is less than the Bohr radius. Since the interaction between Ag and Ag is very small, there is almost no increase in the excitation level of the acceptor. According to the calculation result shown in FIG. 5, the activation energy is 386 meV.

  However, in the Ag concentration range of 1 at% or less, the width of the Ag-O anti-bonding orbital band (excitation level width) is as narrow as 58 meV, and it is difficult to occupy the orbit by electron excitation from the valence band ( Occupancy is suppressed). That is, for example, when the Ag concentration is 1 at% or less, it is suggested that it is difficult to produce a low-resistance p-type ZnO-based semiconductor thin film.

  FIG. 8 shows a model of an Ag-doped ZnO semiconductor crystal when the Ag concentration is 2 at%.

  When the Ag concentration is 2 at%, the interatomic distance of Ag doped in the ZnO semiconductor crystal is, for example, 10.045Å. Note that Ag was substituted in ZnO at the Zn position in ZnO and arranged so that the spatial distribution in the ZnO crystal was uniform.

  Unlike the case where the Ag concentration is 1 at% or less, the interatomic distance between Ag and Ag approaches the Bohr radius (value less than 10.17 cm) of holes. For this reason, interaction begins to occur, and the bandwidth of the acceptor excitation level increases. According to the calculation result shown in FIG. 5, the width of the Ag-O anti-bonding orbital band is 98 meV. For this reason, it is considered that the difficulty of occupying the orbit due to electron excitation from the valence band is eliminated at an Ag concentration of 2 at%.

  On the other hand, according to the result shown in FIG. 5, the activation energy is 348 meV. It can be seen that the interatomic distance between Ag and Ag at an Ag concentration of 2 at% is such a distance that the interaction for increasing the activation energy does not work.

  Therefore, it can be said that the Ag doping concentration should be 2 at% or more in order to reduce the resistance p-type of the ZnO-based semiconductor.

  FIG. 9 shows a model of an Ag-doped ZnO semiconductor crystal when the Ag concentration is 3 at%.

  When the Ag concentration is 3 at%, the interatomic distance of Ag doped in the ZnO semiconductor crystal is, for example, 7.915 Å (interatomic distance between Ag1 and Ag2), 8.539 Å (interatomic distance between Ag2 and Ag3) Distance), 6.169Å (interatomic distance between Ag1 and Ag3). Note that Ag1 to Ag3 are not Zn-substituted in the same (0001) plane, and two of the three interatomic distances between Ag and Ag are, as much as possible, the Bohr radius of the hole (hole). It arrange | positioned so that it might become larger.

  When the Ag concentration is 3 at%, the interatomic distance between Ag and Ag is shorter than the Bohr radius (a value larger than 7.64 mm) (for example, the distance between Ag1 and Ag3 = 6.169 mm). . For this reason, the interaction between Ag and Ag is increased, the acceptor excitation level is increased, and it is difficult to reduce the resistance of the ZnO-based semiconductor to p-type. According to the calculation result shown in FIG. 5, the activation energy is 456 meV. It can be said that the Ag doping concentration needs to be less than 3 at% in order to reduce the resistance p-type of the ZnO-based semiconductor.

  From the calculation results shown in FIG. 5 and the discussion described with reference to FIGS. 7 to 9, the ZnO-based semiconductor is obtained by setting the concentration of Ag doped in the ZnO-based semiconductor to a value of 2 at% or more and less than 3 at%. It is possible to draw a conclusion that it becomes possible to reduce the p-type resistance.

  At this time, the mutual distance of Ag in the p-type ZnO-based semiconductor crystal doped with Ag is larger than 6.169Å and not more than 10.045Å.

  With reference to FIG. 10, the manufacturing method of the Ag dope p-type ZnO type | system | group semiconductor crystal layer by an Example is demonstrated.

After performing thermal cleaning on the Zn-faced ZnO (0001) substrate 11 at 900 ° C. for 30 minutes, the substrate temperature is lowered to 250 ° C. Thereafter, the growth temperature is 250 ° C., the Zn deposition rate F _Zn is 0.15 nm / s, the O radical beam irradiation conditions are RF power 300 W, O ₂ flow rate 2.0 sccm (O flux J _O = 8.1 × 10 ^14). atoms / cm ² s), a 30 nm thick ZnO buffer layer 12 is grown. The growth time is 5 minutes. Then, in order to improve the crystallinity and surface flatness of the buffer layer 12, annealing is performed at 950 ° C. for 30 minutes.

On the ZnO buffer layer 12, a growth temperature of 950 ° C., a Zn deposition rate F _Zn of 0.15 nm / s, an O radical beam irradiation condition of RF power 300 W, an O ₂ flow rate of 2.0 sccm, and a 100 nm thick undoped ZnO Layer 13 is grown. The growth time is 15 minutes.

An Ag-doped ZnO layer is grown on the undoped ZnO layer 13. A growth temperature of 250 ° C., a Zn deposition rate F of _Zn of 0.15 nm / s, an O radical beam irradiation condition of RF power of 300 W, an O ₂ flow rate of 2.0 sccm, an Ag cell temperature T _Ag of 900 ° C., and a thickness of 130 nm of Ag. A doped ZnO layer is grown. This is an example of a growth condition in which the concentration of Ag doped in the ZnO layer is in the range of 2 at% or more and less than 3 at%. The growth time is 15 minutes. Then, annealing treatment for activating impurities (Ag) is performed on the Ag-doped ZnO layer. Annealing is performed at 550 ° C. for 10 minutes in an oxygen atmosphere. Thus, the Ag-doped p-type ZnO crystal layer 14 is formed on the undoped ZnO layer 13.

  The Ag-doped p-type ZnO crystal layer 14 is a low-resistance ZnO-based semiconductor single crystal layer having an Ag concentration of 2 at% or more and less than 3 at%. The inter-Ag distance in the Ag-doped p-type ZnO crystal layer 14 is greater than 6.169 and less than or equal to 10.045.

  Since a low-resistance p-type ZnO-based semiconductor single crystal layer can be realized, a high-quality semiconductor element such as a light-emitting diode can be manufactured.

FIG. 11 is a schematic cross-sectional view of a ZnO based semiconductor light emitting device. On the Zn surface ZnO substrate 1, the growth temperature is 250 ° C., the Zn deposition rate F _Zn is 0.15 nm / s (Zn flux J _Zn = 9.9 × 10 ¹⁴ atoms / cm ² s), and the O radical beam irradiation conditions The ZnO buffer layer 2 having a thickness of 30 nm is grown with an RF power of 300 W and an O ₂ flow rate of 2.0 sccm (O flux J _O = 8.1 × 10 ¹⁴ atoms / cm ² s). In order to improve the crystallinity and surface flatness of the buffer layer, annealing is performed at 950 ° C. for 30 minutes.

On the ZnO buffer layer 2, Zn, O and Ga are simultaneously supplied at a growth temperature of 900 ° C. to grow an n-type ZnO layer 3 having a thickness of 150 nm. Zn deposition rate F _Zn is 0.15 nm / s, O radical beam irradiation conditions are RF power 250 W, O ₂ flow rate 1.0 sccm (O flux J _O = 4.0 × 10 ¹⁴ atoms / cm ² s), Ga The cell temperature _TGa is 460 ° C. The Ga concentration of the n-type ZnO layer 3 is 1.5 × 10 ¹⁸ cm ⁻³ .

On the n-type ZnO layer 3, the growth temperature is 900 ° C., the Zn deposition rate F _Zn is 0.03 nm / s (Zn flux J _Zn = 2.0 × 10 ¹⁴ atoms / cm ² s), and O radical beam irradiation conditions. The RF power is 300 W, the O ₂ flow rate is 2.0 sccm, and an undoped ZnO active layer 4 having a thickness of 15 nm is grown.

The substrate temperature is lowered to 250 ° C., and an Ag-doped ZnO layer 5 is formed on the undoped ZnO active layer 4 as a p-type layer. Zn deposition rate F _Zn is 0.15 nm / s, O radical beam irradiation conditions are RF power 300 W, O ₂ flow rate 2.0 sccm, Ag cell temperature T _Ag is 900 ° C., and a 130 nm thick Ag-doped ZnO layer is grown. (Growth time is 15 minutes), and annealing is performed at 550 ° C. for 10 minutes in an oxygen atmosphere to activate impurities (Ag).

  An n-side electrode 6n is formed on the back surface of the ZnO substrate 1, a p-side electrode 6p is formed on the Ag-doped p-type ZnO layer 5, and a bonding electrode 7 is formed on the p-side electrode 6p. The n-side electrode 6n is formed by laminating a 500 nm thick Au layer on a 10 nm thick Ti layer. The p-side electrode 6p is formed by laminating an Au layer having a thickness of 10 nm on a Ni layer having a size of 300 μm □ and a thickness of 1 nm, and the bonding electrode 7 is an Au layer having a size of 100 μm □ and a thickness of 500 nm. Form. In this manner, a ZnO-based semiconductor light emitting element is manufactured.

  Note that the active layer may have a multiple quantum well structure.

Although the case where ZnO is doped with Ag has been described, ZnO and Mg _x Zn _1-x O (0 ≦ x ≦ 0.6) can perform substantially the same crystal growth. Therefore, it may be applicable to the growth of Ag-doped Mg _x Zn _1-x O (0 ≦ x ≦ 0.6).

In addition, the O radical generated from the plasma of oxygen gas is used as the oxygen source. However, not only oxygen gas but also other gases having strong oxidizing power such as polar oxidants such as ozone, H ₂ O, and alcohol may be used. It is considered possible.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

1 ZnO substrate 2 ZnO buffer layer 3 n-type ZnO layer 4 ZnO active layer 5 Ag-doped p-type ZnO layer 6 n n-side electrode 6 p p-side electrode 7 bonding electrode 11 ZnO substrate 12 ZnO buffer layer 13 undoped ZnO layer 14 Ag-doped p-type ZnO crystal layer 101 Vacuum chamber 102 Zn source gun 103 O source gun 104 Mg source gun 105 Ag source gun 106 Solid source gun 107 Stage 108 Growth substrate 109 Thickness gauge 110 RHEED gun 111 Screen

Claims (2)

  An Ag-doped p-type ZnO-based semiconductor crystal layer doped with 2% or more and less than 3% of Ag in terms of the positive element. An Ag-doped p-type ZnO-based semiconductor crystal layer doped with Ag, wherein an Ag interatomic distance is greater than 6.169Å and 10.045Å or less.