JP2011151240A - Epitaxial wafer, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epitaxial wafer capable of utilizing accumulated manufacturing technology and manufacturing know-how, and suppressing diffusion of p-type impurities, and to provide a method of manufacturing the same. <P>SOLUTION: The epitaxial wafer 1 includes: a semiconductor substrate 10; an n-type clad layer 20 formed on the upper side of the semiconductor substrate 10; an active layer 40 formed above the n-type clad layer 20 and containing C of atomic concentration ≤5.0×10<SP>15</SP>cm<SP>-3</SP>, Mg of atomic concentration of 1.0×10<SP>16</SP>to 1.6×10<SP>16</SP>cm<SP>-3</SP>and Zn of atomic concentration of 1.1×10<SP>16</SP>to 5.0×10<SP>18</SP>cm<SP>-3</SP>; a p-type clad layer 60 including a carbon-doped layer 62 with C doped therein, an undoped layer 64 and a magnesium-doped layer 66 with Mg doped therein; and a p-type cap layer 70 formed on the p-type clad layer 60 and containing Zn. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an epitaxial wafer and an epitaxial wafer manufacturing method. In particular, the present invention relates to an epitaxial wafer for a light emitting device and a method for manufacturing the epitaxial wafer.

Conventionally, in a compound semiconductor epitaxial wafer having a double heterostructure in which at least an n-type cladding layer made of an AlGaInP-based material, an active layer, and a p-type cladding layer are sequentially laminated on an n-type GaAs substrate, a p-type made of an AlGaInP-based material. The p-type impurity in the cladding layer is carbon, and the carrier concentration in the p-type cladding layer is in the range of 8.0 × 10 ¹⁷ cm ⁻³ or more and 1.5 × 10 ¹⁸ cm ⁻³ or less. A wafer is known (for example, refer to Patent Document 1).

  The epitaxial wafer for laser diode described in Patent Document 1 can reduce the diffusion of the p-type impurity into the active layer by using carbon as the p-type impurity in the p-type AlGaInP cladding layer. A high-performance laser diode can be provided.

JP 2009-111160 A

  First, in a compound semiconductor such as AlGaInP, carbon (C), magnesium (Mg), and zinc (Zn) are likely to diffuse in this order. Therefore, when only aiming at suppressing the diffusion of impurities into the active layer, as described in Patent Document 1, it is optimal to use carbon (C) as the impurities. However, conventionally, in the manufacturing process of a light emitting device manufactured from an epitaxial wafer for a light emitting device using Mg or Zn as an impurity, the manufacturing process is based on the assumption that diffusion of Mg or Zn into the active layer occurs. Designed. Therefore, when carbon is used as an impurity, a manufacturing process, a manufacturing technique, and manufacturing know-how designed on the assumption that Mg or Zn is used as an impurity may not be used as it is.

  Accordingly, an object of the present invention is to provide an epitaxial wafer and an epitaxial wafer manufacturing method that can make use of the accumulated manufacturing technology and manufacturing know-how and can suppress the diffusion of p-type impurities.

In order to achieve the above object, the present invention provides a semiconductor substrate, an n-type cladding layer provided above the semiconductor substrate, and an atom of 5.0 × 10 ¹⁵ cm ⁻³ or less provided above the n-type cladding layer. Concentration of carbon, magnesium having an atomic concentration of 1.0 × 10 ¹⁶ cm ⁻³ or more and 1.6 × 10 ¹⁶ cm ⁻³ or less, and 1.1 × 10 ¹⁶ cm ⁻³ or more and 5.0 × 10 ¹⁸ cm ^{−. An} active layer containing zinc having an atomic concentration of ³ or less, a carbon-doped layer provided above the active layer and doped with carbon, an undoped layer provided on the carbon-doped layer and not doped with impurities, An epitaxial wafer comprising a p-type cladding layer provided on an undoped layer and having a magnesium-doped layer doped with magnesium, and a p-type cap layer provided on the p-type cladding layer and containing zinc Is provided.

  In the epitaxial wafer, the semiconductor substrate is an n-type GaAs substrate, the n-type cladding layer, the active layer, and the p-type cladding layer are made of an AlGaInP-based compound semiconductor, and the p-type cap layer is made of p-type GaAs. It is preferable to become.

In the epitaxial wafer, the carbon doped layer contains carbon having an atomic concentration of 1.0 × 10 ¹⁷ cm ⁻³ or more and 8.0 × 10 ¹⁸ cm ⁻³ or less, and the magnesium doped layer is 5.0 × 10 10. ^It contains magnesium having an atomic concentration of ¹⁷ cm ⁻³ or more and 8.0 × 10 ¹⁸ cm ⁻³ or less, and the p-type cap layer is 5.0 × 10 ¹⁷ cm ⁻³ or more and 1.2 × 10 ²⁰ cm ⁻³ or less. It preferably contains an atomic concentration of zinc.

  In the epitaxial wafer, the p-type cladding layer is composed of a carbon-doped layer, an undoped layer, and a magnesium-doped layer, and the carbon-doped layer has a thickness of 5% to 60% of the thickness of the magnesium-doped layer. The undoped layer preferably has a thickness of 5 nm to 10 nm.

  In order to achieve the above object, the present invention provides an n-type GaAs substrate, an n-type cladding layer provided above the n-type GaAs substrate, an active layer provided above the n-type cladding layer, A carbon-doped layer provided above and doped with carbon, an undoped layer provided on the carbon-doped layer and not doped with impurities, and a zinc-doped layer provided on the undoped layer and doped with zinc There is provided an epitaxial wafer including a p-type cladding layer and a p-type cap layer formed on the p-type cladding layer and made of p-type GaAs.

In order to achieve the above object, the present invention provides a semiconductor substrate preparation step for preparing a semiconductor substrate, an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type cap layer above the semiconductor substrate. A semiconductor laminated structure forming step, wherein a p-type cladding layer is provided on the active layer and is doped with carbon, and an undoped layer is provided on the carbon-doped layer and is not doped with impurities. And a magnesium-doped layer provided on the undoped layer and doped with magnesium, and the active layer includes carbon having an atomic concentration of 5.0 × 10 ¹⁵ cm ⁻³ or less, 1.0 × 10 ¹⁶ cm ^{− 3 to} 1.6 × 10 ¹⁶ cm ⁻³ of atomic concentration magnesium and 1.1 × 10 ¹⁶ cm ^{−3 to} 5.0 × 10 ¹⁸ cm ⁻³ of atomic concentration zinc, p-type Cat A method for producing an epitaxial wafer in which the top layer contains zinc is provided.

In the epitaxial wafer manufacturing method, the semiconductor multilayer structure forming step can supply CBr ₄ during the growth of the carbon-doped layer and supply Cp ₂ Mg during the growth of the magnesium-doped layer.

  In the epitaxial wafer manufacturing method, the semiconductor laminated structure forming step may form the undoped layer from GaAs or AlGaAs.

  According to an epitaxial wafer and an epitaxial wafer manufacturing method according to the present invention, an epitaxial wafer and an epitaxial wafer manufacturing method capable of making use of accumulated manufacturing technology and manufacturing know-how and suppressing the diffusion of p-type impurities are provided. it can.

It is a longitudinal section of an epitaxial wafer concerning an embodiment of the invention. It is a figure which shows the carrier concentration distribution of the depth direction of the p-type cladding layer of the epitaxial wafer which concerns on an Example and a comparative example.

[Summary of embodiment]
In an epitaxial wafer for a light emitting device having a double heterostructure on a semiconductor substrate, a semiconductor substrate, an n-type cladding layer provided above the semiconductor substrate, and provided above the n-type cladding layer, 5.0 × Carbon having an atomic concentration of 10 ¹⁵ cm ⁻³ or less, magnesium having an atomic concentration of 1.0 × 10 ¹⁶ cm ⁻³ or more and 1.6 × 10 ¹⁶ cm ⁻³ or less, and 1.1 × 10 ¹⁶ cm ⁻³ or more An active layer containing zinc having an atomic concentration of 5.0 × 10 ¹⁸ cm ⁻³ or less, a carbon-doped layer provided above the active layer, doped with carbon, and provided on the carbon-doped layer, A p-type cladding layer comprising: an undoped layer not doped with impurities; and a magnesium-doped layer provided on the undoped layer and doped with magnesium; and the p-type cladding. An epitaxial wafer is provided comprising a p-type cap layer provided on the layer and comprising zinc.

[Embodiment]
(Configuration of epitaxial wafer 1)
FIG. 1 shows an outline of a longitudinal section of an epitaxial wafer according to an embodiment of the present invention.

  The epitaxial wafer 1 according to the present embodiment can be used as an epitaxial wafer 1 for a light emitting element such as a laser diode (LD) or a light emitting diode (LED). Specifically, the epitaxial wafer 1 includes a semiconductor substrate 10, an n-type cladding layer 20 provided on the semiconductor substrate 10, a first guide layer 30 provided on the n-type cladding layer 20, and the first guide layer 30. An active layer 40 provided on the active layer 40, a second guide layer 50 provided on the active layer 40, a p-type cladding layer 60 provided on the second guide layer 50, and a p-type cap provided on the p-type cladding layer 60. Layer 70. That is, the epitaxial wafer 1 has a double hetero structure.

  Furthermore, the p-type cladding layer 60 is provided above the active layer 40 (that is, on the second guide layer 50), and includes a carbon-doped layer 62 doped with carbon (C) as a p-type impurity, and a carbon-doped layer. And an undoped layer 64 that is not doped with impurities and a magnesium doped layer 66 that is provided on the undoped layer 64 and doped with magnesium (Mg). That is, the carbon doped layer 62, the undoped layer 64, and the magnesium doped layer 66 are provided in this order from the side close to the active layer 40. By providing the carbon doped layer 62 on the side close to the active layer 40, diffusion of Mg doped in the magnesium doped layer 66 into the active layer 40 can be suppressed. That is, the carbon doped layer 62 exhibits a function as a barrier layer that suppresses the diffusion of Mg. Thereby, the diffusion of Mg into the active layer 40 can be suppressed, and the deterioration of the characteristics of devices such as light emitting elements manufactured from the epitaxial wafer 1 can be suppressed.

Here, the carbon doped layer 62 preferably contains carbon having an atomic concentration of 1.0 × 10 ¹⁷ cm ⁻³ or more and 8.0 × 10 ¹⁸ cm ⁻³ or less, and 1.0 × 10 ¹⁷ cm ⁻³ or more. More preferably, it contains carbon having an atomic concentration of 6.0 × 10 ¹⁸ cm ⁻³ or less, and contains carbon having an atomic concentration of 1.0 × 10 ¹⁷ cm ⁻³ or more and 3.0 × 10 ¹⁸ cm ⁻³ or less. Is particularly preferred. The magnesium doped layer 66 preferably contains magnesium having an atomic concentration of 5.0 × 10 ¹⁷ cm ⁻³ or more and 8.0 × 10 ¹⁸ cm ⁻³ or less, and 8.0 × 10 ¹⁷ cm ⁻³ or more and 8 or more. preferably comprises magnesium .0 × ¹⁰ 18 ^{cm -3} or less in atomic concentration, in particular to contain magnesium of 8.0 × ¹⁰ 17 ^{cm -3} or more 3.0 × ¹⁰ 18 ^{cm -3} or less of atomic concentration preferable. Although the undoped layer 64 is not doped with impurities, unavoidable impurities may be included. The p-type cladding layer 60 preferably has a three-layer structure including a carbon doped layer 62, an undoped layer 64, and a magnesium doped layer 66. In this case, the carbon doped layer 62 preferably has a thickness of 5% to 60% of the thickness of the magnesium doped layer 66 (for example, a thickness of 16 μm). This is because when the thickness of the carbon doped layer 62 is less than 5% of the thickness of the magnesium doped layer 66, the carbon doped layer 62 cannot sufficiently suppress the diffusion of Mg. Further, when the thickness of the carbon doped layer 62 exceeds 60% of the thickness of the magnesium doped layer 66, the diffusion of Mg into the active layer 40 is substantially eliminated. This is because the process settings of the process may need to be changed.

  The undoped layer 64 has a thickness of 5 nm or more for the purpose of suppressing diffusion of Mg in the magnesium doped layer 66 and impurities (for example, Zn) in the p-type cap layer 70 to the active layer 40 side. At the same time, it is preferable to have a thickness of 10 nm or less in order to prevent it from functioning as an electrically conductive resistance layer. In the present embodiment, the undoped layer 64 is formed from GaAs or AlGaAs. Therefore, when the thickness of the undoped layer exceeds a predetermined thickness, the average composition of the p-type cladding layer may not be the composition of the AlGaInP-based compound semiconductor. In this case, it is preferable that the undoped layer has a thickness of 10 nm or less because the light emission characteristics (for example, emission angle) of a light emitting element manufactured from an epitaxial wafer, for example, LD, may deviate from the design value.

  The semiconductor substrate 10 is made of a III-V group compound semiconductor, and can be made of, for example, n-type GaAs. Each semiconductor layer (except for the p-type cap layer 70) provided on the semiconductor substrate 10 can be formed of an AlGaInP-based compound semiconductor. The p-type cap layer 70 can be formed from, for example, p-type GaAs. A p-side electrode made of a material that makes ohmic contact with the p-type cap layer 70 is provided in a partial region on the p-type cap layer 70, and the n-type cladding layer 20 of the semiconductor substrate 10, that is, the back side of the semiconductor substrate 10. An n-side electrode made of a material that makes ohmic contact with the semiconductor substrate 10 can be provided on substantially the entire surface opposite to the surface in contact with the semiconductor substrate 10.

  The n-type cladding layer 20 is doped with silicon (Si) as an n-type impurity. The p-type cap layer 70 is doped with zinc (Zn) as a p-type impurity. The p-type cap layer 70 can be doped with C together with Zn. By co-doping Zn and C into the p-type cap layer 70, the amount of Zn doped into the p-type cap layer 70 can be reduced, and the Mg doped into the magnesium-doped layer 66 and the p-type cap layer Interdiffusion with Zn doped in 70 can be reduced.

In the present embodiment, the active layer 40 includes carbon having an atomic concentration of 5.0 × 10 ¹⁵ cm ⁻³ or less and 1.0 × 10 ¹⁶ cm ⁻³ or more and 1.6 × 10 ¹⁶ cm ⁻³ or less. And magnesium having an atomic concentration of 1.1 × 10 ¹⁶ cm ⁻³ or more and 5.0 × 10 ¹⁸ cm ⁻³ or less. Further, the p-type cap layer 70 preferably contains zinc having an atomic concentration of 5.0 × 10 ¹⁷ cm ⁻³ or more and 1.2 × 10 ²⁰ cm ⁻³ or less, and 8.0 × 10 ¹⁷ cm ⁻³ or more. More preferably, it contains zinc having an atomic concentration of 4.0 × 10 ¹⁹ cm ⁻³ or less.

(Modification)
The magnesium doped layer 66 included in the p-type cladding layer 60 may be a zinc doped layer doped with Zn. Further, the magnesium doped layer 66 may be a carbon-magnesium mixed doped layer in which C and Mg are co-doped. Further, a buffer layer made of GaAs or the like can be provided between the semiconductor substrate 10 and the n-type cladding layer 20. Further, the first guide layer 30 and the second guide layer 50 may be omitted. In addition, a light emitting layer may be provided instead of the active layer 40, and the light emitting layer may have a quantum well structure, a multiple quantum well structure, a strained quantum well structure, or the like. The p-type cap layer 70 can also be formed from a compound semiconductor such as AlGaAs or GaP.

(Method of manufacturing epitaxial wafer 1)
Epitaxial wafer 1 according to the present embodiment can be manufactured using a metal organic vapor phase epitaxy method (MOVPE method). That is, after the semiconductor substrate 10 is installed in the reactor of the MOVPE apparatus, the inside of the reactor is controlled to a predetermined atmosphere and a predetermined pressure. Subsequently, in this state, the semiconductor substrate 10 is heated to a predetermined temperature. The n-type cladding layer 20, the first guide layer 30, the active layer 40, the second guide layer 50, the p-type cladding layer 60, and the p-type cap layer 70 are required for epitaxial growth on the heated semiconductor substrate 10. A group III source gas, a group V source gas, a carrier gas, and a dopant source gas are appropriately supplied. Thereby, the epitaxial wafer 1 is manufactured.

As group III source gases, Al (CH ₃ ) ₃ [trimethylaluminum: TMAl], Al (C ₂ H ₅ ) ₃ [triethylaluminum], Ga (CH ₃ ) ₃ [trimethylgallium: TMGa], Ga ( Use of an organometallic compound including at least one of C ₂ H ₅ ) ₃ [triethylgallium], In (CH ₃ ) ₃ [trimethylindium: TMIn], and In (C ₂ H ₅ ) ₃ [triethylindium] Can do.

Further, as the group V source gas, AsH ₃ [arsine], PH ₃ [phosphine], TBP [tertiary butyl phosphine], As (CH ₃ ) ₃ [trimethylarsine], TBA [tertiary butyl arsine], and NH ₃ Gas containing at least one kind such as [ammonia] can be used. As the carrier gas, a gas containing at least one kind such as H ₂ [hydrogen], N ₂ [nitrogen], and Ar [argon] can be used.

The source gas of the n-type dopant includes at least one of Si ₂ H ₆ [disilane], SiH ₄ [silane], H ₂ Se [hydrogen selenide], Te (C ₂ H ₅ ) _{2 and the} like. Gas can be used. The doping of carbon (C) as a p-type dopant is performed by autodoping from an organometallic compound gas by adjusting the V / III ratio, which is the ratio of the Group V source gas concentration to the Group III source gas concentration, or the growth temperature. It can be carried out by autodoping from an organometallic compound gas by adjusting the above. Alternatively, CBr ₄ [carbon tetrabromide] gas can be used as the source gas for the p-type dopant.

Further, Cp ₂ Mg [biscyclopentadienylmagnesium] can be used for doping the p-type dopant Mg. Further, DEZ [diethyl zinc] or DMZ [dimethylzinc] can be used for doping with the p-type dopant Zn.

  A p-side electrode and an n-side electrode can be formed on the obtained epitaxial wafer 1. Each of the p-side electrode and the n-side electrode can be formed using a photolithography method, a vacuum evaporation method, a sputtering method, or the like.

(About the function of the p-type cladding layer 60)
In the present embodiment, the p-type cladding layer 60 is formed having a three-layer structure of a carbon doped layer 62, an undoped layer 64, and a magnesium doped layer 66. Since the undoped layer 64 is sandwiched between the magnesium doped layer 66 and the carbon doped layer 62, the undoped layer 64 suppresses Mg in the magnesium doped layer 66 from diffusing to the active layer 40 side. More specifically, by forming the carbon doped layer 62 on the active layer 40 side (that is, in the vicinity of the active layer 40), the carbon doped layer 62 functions as a barrier layer that suppresses Mg diffusion into the active layer 40. Thereby, since the carbon dope layer 62 suppresses the diffusion of Mg into the active layer 40, it is possible to suppress the deterioration of the device characteristics of the light emitting element manufactured from the epitaxial wafer 1. In the light emitting device manufactured from the epitaxial wafer 1, when the p-type cladding layer 60 needs to be doped with a high concentration of impurities, or when the temperature during epitaxial growth of the epitaxial wafer 1 needs to be high, Mg is more Although it becomes easy to diffuse to the active layer 40 side, the diffusion of Mg to the active layer 40 side can be suppressed by the undoped layer 64.

  Further, C in the carbon doped layer 62 is less likely to diffuse than Mg, and C is less likely to diffuse into the active layer 40. Therefore, Mg doped in the magnesium doped layer 66 and C doped in the carbon doped layer 62 tend to stay in the p-type cladding layer 60, so that the carrier concentration in the entire p-type cladding layer 60 can be kept substantially uniform. .

  Further, when increasing the atomic concentration of Mg in the active layer 40, the thickness of the carbon doped layer 62 and the carbon atomic concentration of the carbon doped layer 62 are reduced. That is, when the purpose is to utilize the manufacturing process, manufacturing technology, manufacturing know-how of the conventional light emitting device as it is, and when it is necessary to adjust the diffusion of Mg to the active layer 40 to the same level as before, The thickness of the carbon doped layer 62 and the carbon atom concentration of the carbon doped layer 62 can be reduced, and the atomic concentration of Mg in the active layer 40 can be increased.

(Effect of embodiment)
In epitaxial wafer 1 according to the present embodiment, p-type cladding layer 60 is formed of a three-layer structure of carbon-doped layer 62, undoped layer 64, and magnesium-doped layer 66, and C is less likely to diffuse than Mg. Therefore, compared with the case where the p-type cladding layer 60 is doped only with Mg, the diffusion of the p-type impurity into the active layer 40 in contact with the p-type cladding layer 60 can be reduced. Further, since the p-type cladding layer 60 has the undoped layer 64 made of GaAs or AlGaAs, the magnesium doped layer 66 is doped at the heterojunction interface between the undoped layer 64 and the carbon doped layer 62 or the magnesium doped layer 66. Further, Mg doped in the Mg and the p-type cap layer 70 can be efficiently trapped. Thereby, it can suppress to some extent that Mg and Zn diffuse into the active layer 40. Therefore, according to epitaxial wafer 1 according to the present embodiment, diffusion of p-type impurities into active layer 40 can be suppressed to some extent, and a certain amount of p-type impurities can be diffused into active layer 40. Manufacturing processes, manufacturing techniques, and manufacturing know-how designed on the premise of using Mg or Zn can be utilized.

  As described above, when the epitaxial wafer 1 according to the present embodiment is used, light emission with a low operating current value and high reliability can be obtained without greatly changing the conventional manufacturing process, manufacturing technology, and manufacturing know-how. An element can be provided.

Further, when Zn or Mg is used as the p-type impurity of the p-type cladding layer as in the prior art, the crystallinity of the active layer 40 is reduced due to the diffusion of Zn or Mg into the active layer 40. As a result, when the characteristics of the active layer 40 are evaluated by photoluminescence (PL) measurement, the half-value width of the emission spectrum is abruptly widened with an increase in the doping amount of Zn or Mg. Therefore, in the conventional wafer, the carrier concentration of the p-type cladding layer is suppressed to about 4.0 × 10 ¹⁷ cm ⁻³ . However, since the carrier concentration is kept low, it is difficult to reduce the operating current value of a light emitting device manufactured from a conventional wafer. On the other hand, in the epitaxial wafer 1 according to the present embodiment, even if the carrier concentration of the p-type cladding layer 60 (for example, the magnesium doped layer 66) is set to 9.0 × 10 ¹⁷ cm ⁻³ or more, the inside of the carbon doped layer 62 Thus, most of the diffusion of Mg into the active layer 40 can be stopped. Therefore, the diffusion of Mg into the active layer 40 is less than that in the prior art, and the deterioration of the crystallinity of the active layer 40 due to the diffusion of Mg into the active layer 40 can be suppressed. Thereby, according to the epitaxial wafer 1 which concerns on this Embodiment, when the characteristic of the active layer 40 is evaluated by PL measurement, the result which shows that the half value width of PL light emission is maintained narrow will be obtained.

  In the example, an epitaxial wafer for red LD used as a light source for reading and writing of DVD was manufactured. The structure of the epitaxial wafer according to the example is the same as the structure described in the embodiment (for example, see FIG. 1).

Specifically, the epitaxial wafer according to the example is formed on an n-type GaAs substrate (thickness: 500 μm, target carrier concentration: 8.0 × 10 ¹⁷ cm ⁻³ ) and Si-doped n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P n-type cladding layer (however, thickness: 2.5 μm, target carrier concentration: 8.0 × 10 ¹⁷ cm ⁻³ ), A first guide layer (thickness: 0.02 μm) made of undoped (Al _0.3 Ga _0.7 ) _0.5 In _0.5 P, and undoped (Al _0.05 Ga _0.95 ) an active layer composed of _0.5 an in _0.5 P, a second guide layer composed of undoped _{(Al 0.3 Ga 0.7) 0.5 in} 0.5 P ( where thickness: 0.02 [mu] m) When, the C-doped p-type _(Al 0.7 _{Ga 0.3) .5} an In _0.5 carbon-doped layer made of P (where thickness of 0.4 .mu.m, the carrier concentration and the target: 6.0 × ¹⁰ 18 ^{cm -3)} and, undoped AlGaAs layer (however, thickness: 10 mg) and a Mg-doped p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P-doped magnesium doped layer (thickness: 1.6 μm, target carrier concentration: 6 0.0 × 10 ¹⁸ cm ⁻³ ) and a p-type cap layer made of C-type and Zn-doped p-type GaAs (thickness: 1.5 μm, target carrier concentration: 1.2 × 10 ²⁰ cm ⁻³⁾ ) And epitaxially grown in this order.

  The epitaxial wafer according to the example was manufactured using the MOVPE method. That is, an n-type GaAs substrate is installed in a reactor of a MOVPE apparatus, the inside of the reactor is controlled to a predetermined atmosphere and a predetermined pressure, and then the n-type GaAs substrate is heated to a predetermined temperature, The group III source gas, the group V source gas, the carrier gas, and the dopant source gas required for the epitaxial growth of the first guide layer, the active layer, the second guide layer, the p-type cladding layer, and the epitaxial layer of the p-type cap layer are appropriately selected. Supplied and manufactured.

  Specifically, the epitaxial growth temperature (however, the temperature of the n-type GaAs substrate surface measured by a radiation thermometer installed on the surface of the reactor facing the n-type GaAs substrate) is set to 800 ° C., and the growth pressure (that is, inside the reactor) Pressure) was set to about 10666 Pa (80 Torr). Also, hydrogen was used as the carrier gas.

  The flow rates of the source gases supplied into the reactor during the epitaxial growth of each epitaxial layer are as follows.

(N-type cladding layer)
TMG: 0.012 L / min, TMA: 0.004 L / min, TMI: 0.02 L / min, Si ₂ H ₆ : 0.51 L / min, PH ₃ : 1.8 L / min

(First guide layer and second guide layer)
TMG: 0.014 L / min, TMA: 0.003 L / min, TMI: 0.02 L / min, PH ₃ : 1.8 L / min

(Active layer)
TMG: 0.016 L / min, TMA: 0.002 L / min, TMI: 0.024 L / min, PH ₃ : 1.8 L / min

(Carbon doped layer)
TMG: 0.012 L / min, TMA: 0.004 L / min, TMI: 0.02 L / min, CBr ₄ : 0.22 L / min, PH ₃ : 1.8 L / min

(Undoped layer)
TMG: 0.052 L / min, TMA: 0.02 L / min, AsH ₃ : 0.5 L / min

(Magnesium doped layer)
TMG: 0.01 L / min, TMA: 0.005 L / min, TMI: 0.02 L / min, Cp ₂ Mg: 0.26 L / min, PH ₃ : 1.8 L / min

(P-type cap layer)
TMG: 0.012 L / min, DEZ: 0.9 L / min, AsH ₃ : 2 L / min

(Comparative example)
As an epitaxial wafer according to a comparative example, an epitaxial wafer having a p-type cladding layer of Mg-doped p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P was manufactured. That is, the epitaxial wafer according to the comparative example has the same configuration as the epitaxial wafer according to the example except that the configuration of the p-type cladding layer is different from that of the epitaxial wafer according to the example.

(Comparison of the epitaxial wafer according to the example and the epitaxial wafer according to the comparative example)
For each of the epitaxial wafers according to Examples and Comparative Examples, the impurity concentration distribution of impurities was measured from the p-type cladding layer to the active layer.

  FIG. 2 shows the carrier concentration distribution in the depth direction of the p-type cladding layer of the epitaxial wafer according to the example and the comparative example.

In FIG. 2, the interface between the second guide layer and the active layer is defined to a depth of “0”. The active layer side is negative and the second guide layer side is positive. As can be seen from FIG. 2, the Mg concentration in the active layer is lower in the epitaxial wafer according to the example than in the epitaxial wafer according to the comparative example. The target carrier concentration of the p-type cladding layer in the epitaxial wafer according to the example and the target carrier concentration of the p-type cladding layer in the epitaxial wafer according to the comparative example are both 6.0 × 10 ¹⁸ cm ⁻³ . is there. However, in the p-type cladding layer of the comparative example, since Mg is doped up to the interface between the p-type cladding layer and the second guide layer, it was measured that a large amount of Mg was diffused in the active layer.

  On the other hand, in the epitaxial wafer according to the example, the p-type cladding layer has a carbon doped layer on the active layer side, and an undoped layer is provided between the magnesium doped layer and the carbon doped layer. Referring to FIG. 2, the diffusion of the magnesium doped layer (ie, the region having a depth of 30.0 nm or more and 40.0 nm or less in FIG. 2) into the active layer of Mg becomes the carbon doped layer (ie, the depth 20 of FIG. 2). It was measured that it was suppressed by a region of 0.0 nm or more and 30.0 nm or less. That is, in the examples, it was measured that the Mg concentration in the active layer was lower than in the comparative example.

Next, LD was produced using each epitaxial wafer concerning an example and a comparative example. And the operating current value of produced LD was measured, respectively. As a result, the operating current value I _op of the LD manufactured from the epitaxial wafer according to the example was 67 mA, and the operating current value I _op of the LD manufactured from the epitaxial wafer according to the comparative example was 80 mA. Therefore, according to the epitaxial wafer which concerns on an Example, it was confirmed that the operating current value of LD produced from the said epitaxial wafer can be restrained low, and the improvement of LD reliability and lifetime can be aimed at.

  Further, in the epitaxial wafer according to the example, the thickness of the carbon doped layer and the carbon carrier concentration of the carbon doped layer were adjusted so that the diffusion of Mg into the active layer was optimized, so that the manufacturing process of the light emitting device There is no need to change the process settings. Therefore, in the manufacture of the light emitting device using the epitaxial wafer according to the example, it was possible to make use of the manufacturing technology and manufacturing know-how accumulated so far and to suppress the diffusion of the p-type impurity to the active layer to some extent.

  Note that an LED having high reliability and a long lifetime can be manufactured as a light emitting element from the epitaxial wafer according to the embodiment.

  While the embodiments and examples of the present invention have been described above, the embodiments and examples described above do not limit the invention according to the claims. It should be noted that not all combinations of features described in the embodiments and examples are necessarily essential to the means for solving the problems of the invention.

1 epitaxial wafer 10 semiconductor substrate 20 n-type cladding layer 30 first guide layer 40 active layer 50 second guide layer 60 p-type cladding layer 62 carbon doped layer 64 undoped layer 66 magnesium doped layer 70 p type cap layer

Claims (8)

A semiconductor substrate;
An n-type cladding layer provided above the semiconductor substrate;
Provided above the n-type cladding layer, carbon having an atomic concentration of 5.0 × 10 ¹⁵ cm ⁻³ or less, and atoms of 1.0 × 10 ¹⁶ cm ⁻³ or more and 1.6 × 10 ¹⁶ cm ⁻³ or less An active layer comprising magnesium at a concentration and zinc at an atomic concentration of 1.1 × 10 ¹⁶ cm ⁻³ or more and 5.0 × 10 ¹⁸ cm ⁻³ or less;
Provided above the active layer, carbon doped layer doped with carbon, provided on the carbon doped layer, undoped layer not doped with impurities, provided on the undoped layer, doped with magnesium A p-type cladding layer having a magnesium doped layer;
An epitaxial wafer provided on the p-type cladding layer and comprising a p-type cap layer containing zinc. The semiconductor substrate is an n-type GaAs substrate;
The n-type cladding layer, the active layer, and the p-type cladding layer are made of an AlGaInP-based compound semiconductor,
The epitaxial wafer according to claim 1, wherein the p-type cap layer is made of p-type GaAs. The carbon-doped layer includes the carbon having an atomic concentration of 1.0 × 10 ¹⁷ cm ⁻³ or more and 8.0 × 10 ¹⁸ cm ⁻³ or less,
The magnesium-doped layer includes the magnesium having an atomic concentration of 5.0 × 10 ¹⁷ cm ⁻³ or more and 8.0 × 10 ¹⁸ cm ⁻³ or less,
The epitaxial wafer according to claim 2, wherein the p-type cap layer contains the zinc having an atomic concentration of 5.0 × 10 ¹⁷ cm ⁻³ or more and 1.2 × 10 ²⁰ cm ⁻³ or less. The p-type cladding layer comprises the carbon-doped layer, the undoped layer, and the magnesium-doped layer;
The carbon-doped layer has a thickness of 5% to 60% of the thickness of the magnesium-doped layer;
The epitaxial wafer according to claim 3, wherein the undoped layer has a thickness of 5 nm to 10 nm. an n-type GaAs substrate;
An n-type cladding layer provided above the n-type GaAs substrate;
An active layer provided above the n-type cladding layer;
Provided above the active layer, carbon doped layer doped with carbon, provided on the carbon doped layer, undoped layer not doped with impurities, provided on the undoped layer, doped with zinc A p-type cladding layer comprising a zinc-doped layer;
An epitaxial wafer comprising a p-type cap layer made of p-type GaAs and provided on the p-type cladding layer. A semiconductor substrate preparation step of preparing a semiconductor substrate;
A semiconductor multilayer structure forming step of sequentially forming an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type cap layer above the semiconductor substrate;
The p-type cladding layer is provided on the active layer and doped with carbon, an undoped layer provided on the carbon-doped layer and not doped with impurities, and magnesium provided on the undoped layer. Having a magnesium-doped layer doped with
The active layer includes carbon having an atomic concentration of 5.0 × 10 ¹⁵ cm ⁻³ or less, magnesium having an atomic concentration of 1.0 × 10 ¹⁶ cm ⁻³ or more and 1.6 × 10 ¹⁶ cm ⁻³ or less, 1 1 × 10 ¹⁶ cm ⁻³ or more and 5.0 × 10 ¹⁸ cm ⁻³ or less of an atomic concentration of zinc,
The manufacturing method of the epitaxial wafer in which the said p-type cap layer contains the said zinc. The method for producing an epitaxial wafer according to claim 6, wherein the semiconductor multilayer structure forming step supplies CBr ₄ during the growth of the carbon doped layer and supplies Cp ₂ Mg during the growth of the magnesium doped layer.   8. The method of manufacturing an epitaxial wafer according to claim 7, wherein in the semiconductor multilayer structure forming step, the undoped layer is formed from GaAs or AlGaAs.

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