JP2003179258A - Semiconductor light emitting element and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the cost of a gallium nitride compound semiconductor light emitting element and to reduce an operation voltage. <P>SOLUTION: A buffer layer 2 including phosphorous, which functions as n-type impurity on silicon, is formed on an n-type conductive silicon semiconductor substrate where n-type impurity is doped. A light emitting function semiconductor region 3 including a gallium semiconductor layer is disposed on the buffer layer 2. An anode electrode 4 is disposed on the upper face of the semiconductor region 3 and a cathode electrode 5 is disposed on the lower face of the substrate 1. An inversion layer in the silicon substrate is prevented from being formed by phosphorous. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device using a nitride compound semiconductor and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, GaN, GaAlN, INGa
A semiconductor light emitting device such as a blue light emitting diode using a gallium nitride-based compound semiconductor such as N or InGaAlN has received attention. A typical conventional gallium nitride-based light emitting device is
A structure in which a gallium nitride compound semiconductor layer is formed on an insulating substrate made of sapphire, that is, a substrate, and a pair of electrodes is arranged on the upper surface of the element, or a gallium nitride compound is formed on a low resistance substrate made of silicon carbide. It has a structure in which a semiconductor layer is formed and a pair of electrodes is arranged on the upper surface and the lower surface of the element.

As is well known, the above-described light emitting device is formed by dicing, scribing, and dicing a wafer on which a large number of devices are formed.
It is manufactured by cutting out into chips by cleavage. At this time, since the substrate made of sapphire or the like has high hardness, it was difficult to perform this dicing favorably and with good productivity. Furthermore, since sapphire and the like are expensive themselves,
It was also disadvantageous in terms of material cost.

Therefore, a semiconductor light emitting device in which a low resistance substrate made of silicon is used in place of the substrate made of sapphire or silicon carbide and a nitride compound semiconductor layer is formed on the substrate is considered. Since the hardness of silicon is not as high as that of sapphire, the dicing process and the like can be performed favorably and with good productivity. Further, in the light emitting device using the low resistance substrate, since the pair of electrodes can be formed in the thickness direction of the semiconductor substrate, it is expected that the resistance value of the current path is reduced and the power consumption and the operating voltage are reduced. Was done.

[0005]

By the way, when a nitride-based compound semiconductor layer is formed on a low-resistance substrate, if the low-resistance substrate is composed of an n-type silicon substrate, the nitride formed on this substrate Based compound semiconductors (GaN, GaAlN,
InGaN, InGaAlN, etc.), which are the constituent elements of Group 3, aluminum, gallium, indium, etc. diffuse into the silicon substrate by heat treatment during film growth. Since these Group 3 constituent elements function as p-type impurities (acceptor impurities) with respect to n-type silicon, when diffused into the n-type silicon substrate, the surface side of the silicon substrate (the boundary with the nitride-based compound semiconductor) The p-type semiconductor region is generated by reversing the conductivity type of the surface. As a result, an npn structure is produced by the combination of the n-type buffer layer or the n-type light emitting layer and the pn junction of the silicon substrate. That is, the n-type semiconductor region, the p-type semiconductor region, and the n-type semiconductor region are stacked from the lower surface side of the silicon substrate. Therefore, the resistance value of the current path of the light emitting element is increased, and the expected effects of power consumption reduction and operating voltage reduction cannot be obtained.

Therefore, an object of the present invention is to provide a nitride-based compound semiconductor light emitting device capable of reducing power consumption and operating voltage to a high level, and a method for manufacturing the same.

[0007]

SUMMARY OF THE INVENTION To solve the above problems and to achieve the above objects, the present invention provides a predetermined conductivity type which is made of silicon or a silicon compound containing conductivity determining impurities and has a low resistivity. And a semiconductor substrate adjacent to one main surface of the substrate, comprising a nitride-based compound semiconductor, and containing an element that functions as an impurity of the same conductivity type as the predetermined conductivity type of the substrate with respect to the silicon semiconductor. A buffer layer, a semiconductor region adjacent to the buffer layer for obtaining a light emitting function and having a plurality of nitride-based compound semiconductor layers, and a first region disposed on the front surface side of the semiconductor region. The present invention relates to a semiconductor light emitting device, comprising an electrode and a second electrode arranged on the other main surface side of the substrate. The semiconductor light emitting device of claim 1 is preferably manufactured by the method of claim 2 or 3.

The predetermined conductivity type in the invention of each claim of the present application is n-type or p-type. When the semiconductor substrate is n-type containing n-type impurities, the impurity of a predetermined conductivity type with respect to the silicon semiconductor included in the buffer layer or the nitride-based compound semiconductor layer for obtaining the light emitting function is, for example, phosphorus (P), Arsenic (A
s), antimony (Sb) and other group 5 elemental donor impurities. When the semiconductor substrate is a p-type substrate containing p-type impurities, the impurities contained in the buffer layer or the light-emitting functional nitride compound semiconductor layer are acceptor impurities made of a Group 3 element such as boron (B). The buffer layer is, for example, a single layer such as AlNP or AlGaInNP, or DBR.
It may be a combination of a plurality of layers such as a reflective film. The buffer layer preferably has the same conductivity type as the substrate. The semiconductor region for obtaining the light emitting function preferably has an n-type semiconductor layer, that is, an n-clad layer, an active layer, and a p-type semiconductor layer, that is, a p-type clad layer.

[0009]

According to the invention of each claim, the element functioning as an impurity of a predetermined conductivity type with respect to the silicon semiconductor contained in the buffer layer or the light emitting functional semiconductor layer prevents formation of the inversion layer on the substrate. As a result, generation of unnecessary pn junction is prevented, the resistance value of the forward current path of the light emitting element can be kept small, and the power consumption and operating voltage of the light emitting element can be reduced to a high level.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a gallium nitride-based compound blue light emitting diode as a semiconductor light emitting device according to one embodiment of the present invention will be described with reference to FIG.

A light emitting diode according to an embodiment of the present invention shown in FIG. 1 is a semiconductor substrate 1 having low resistance, that is, conductivity, made of a silicon single crystal containing impurities of a first conductivity type.
A buffer layer 2 made of a 3-5 group compound semiconductor containing an element that functions as a first conductivity type impurity with respect to a silicon semiconductor, a 3-5 group compound semiconductor region 3 for obtaining a light emitting function, and a first electrode And an anode electrode 4 and a cathode electrode 5 as a second electrode. The semiconductor region 3 having a light emitting function has a plurality of gallium nitride-based compound semiconductor layers containing gallium and nitrogen as main components. That is, the light emitting functional semiconductor region 3 includes the n-type semiconductor layer 6 made of n-type GaN (gallium nitride) and the p-type InGaN.
The active layer 7 made of (gallium indium nitride) and the p-type semiconductor layer 8 made of p-type GaN (gallium nitride) are sequentially laminated. The n-type semiconductor layer 6 has a function of an n-type clad layer, and the p-type semiconductor layer 8 has a function of a p-type clad layer. The buffer layer 2 and the semiconductor region 3 having a light emitting function are formed by sequentially epitaxially growing the crystal orientation on the substrate 1.

The substrate 1 contains As (arsenic) of 5 × 10 ¹⁸ cm ^{−3 to} 5 × 10 as n-type (first conductivity type) impurities.
Included in a relatively high concentration of about ¹⁹ cm ⁻³ , 0.001Ω
A conductive substrate having a resistivity of about cm to 0.01 Ωcm. The substrate 1 having a relatively low resistivity functions as a current path between the anode electrode 4 and the cathode electrode 5.
The substrate 1 has a relatively large thickness of about 350 μm, and has an n-type semiconductor region 6, an active layer 7, and a p-type semiconductor region 8.
And functions as a support for the semiconductor region 3 and the buffer layer 2 having a light emitting function.

[0013] The buffer layer 2 formed on the main surface of one substrate 1, wherein the chemical formula _{Al x Ga y In 1-Xy} N a P 1-a, x and y 0 <x ≦ 1 0 ≦ y < A numerical value satisfying 10 <x + y ≦ 1, a is a value satisfying 0 <a <1, and a compound semiconductor of group 3-5, which can be represented by, includes an n-type impurity (for example, Si). desirable. The buffer layer 2 of this embodiment has x =
Al _0.7 G corresponding to 0.7, y = 0.2, a = 0.2
a silicon substrate made of a compound semiconductor composed of a _0.2 In _0.1 N _0.2 P _0.8 and doped with silicon (Si).
Has a function of favorably growing the nitride-based compound semiconductor region 3 (n-type semiconductor region 6, active layer 7, p-type semiconductor region 8) thereon. That is, it is difficult to directly grow a nitride compound semiconductor, for example, a semiconductor region of GaN, AlGaN, or the like on the surface of the substrate 1 made of silicon, but if the film is grown via the buffer layer 2, these The semiconductor region can be formed with good crystallinity. This is because Al _x Ga _y In
_{This is because the 1-xy} NaP _1-a buffer layer 2 can favorably inherit the plane orientation of the silicon substrate 1, and the nitride-based compound semiconductor region 3 having good crystallinity can be grown on this surface. is there.

According to the present invention, the n-type buffer layer 2 doped with silicon as the n-type impurity contains phosphorus (P), which is an element functioning as an n-type impurity, that is, a donor impurity, with respect to the silicon substrate 1. Including. Phosphorus prevents the surface of the n-type silicon substrate 1 from inverting to the p-type. That is, aluminum that constitutes the buffer layer 2 is a Group 3 element and functions as an acceptor impurity, that is, a p-type impurity with respect to the silicon substrate 1. Therefore, when the buffer layer 2 is formed by the vapor deposition method, aluminum is an n-type silicon substrate 1
When diffused into the substrate, a p-type layer may be formed on the surface of the silicon substrate 1. However, according to the invention, the buffer layer 2
Including phosphorus as a donor impurity, that is, an n-type impurity, prevents phosphorus as a donor impurity from diffusing into the silicon substrate 1 together with aluminum as an acceptor impurity, and prevents the surface of the silicon substrate 1 from being inverted to p-type. Therefore, the silicon substrate 1 maintains the n-type throughout the thickness direction.

In the light emitting device of this embodiment, the buffer layer 2
Is set to, for example, about 20 nm so that the gallium nitride-based compound semiconductor region 3 can be formed on this surface with good crystallinity. The thickness of the buffer layer 2 is 0.
If the thickness is less than 5 nm, the original function of the buffer layer 2, that is, the function of growing a gallium nitride-based compound semiconductor having good crystallinity on the surface cannot be sufficiently exhibited. on the other hand,
When the thickness of the buffer layer 2 is increased, the crystallinity of the gallium nitride-based compound semiconductor film-grown on this surface is improved, and the generation of pits (minute holes) can be suppressed. But,
For example, if the buffer layer 2 is formed so thick as to exceed 100 nm, the buffer layer 2 is cracked, which is not desirable. Therefore, the preferable thickness of the buffer layer 2 is 0.5 nm to 100 nm.
nm.

The n-type semiconductor layer 6 formed on the upper surface of the buffer layer 2, that is, the n-type cladding layer is made of n-type GaN and is formed on the surface of the buffer layer 2 to a thickness of about 500 nm. The concentration of n-type impurities (for example, silicon) in the n-type semiconductor region 6 is 3 × 10 ¹⁸ cm ⁻³ , which is lower than the concentration of n-type impurities in the silicon substrate 1.

The active layer 7 formed on the n-type semiconductor region 6 is made of p-type GaInN, has a thickness of about 500 nm, and has a p-type impurity concentration of 3 × 10 ¹⁷ cm ^-3 . This p-type impurity is magnesium.

The p-type semiconductor region or p-type cladding layer 8 formed on the active layer 7 is made of p-type GaN and has a thickness of about 500.
and a p-type impurity concentration of 3 × 10 ¹⁸ cm ⁻³ . This p-type impurity is magnesium.

The anode electrode 4 as the first electrode is connected to a part of the upper surface of the p-type semiconductor layer 8, that is, the central portion.
Therefore, the light emitted from the light emitting functional semiconductor region 3 can be extracted from above. A well-known current diffusion layer, contact layer, and current limiting layer can be formed on the p-type semiconductor region 8. Further, the anode electrode 4 can be formed through a known light-transmitting conductive film. Second
The cathode electrode 5 as an electrode of is connected to the lower surface of the substrate 1.

When manufacturing the light emitting diode of FIG.
First, the n-type Si substrate 1 is prepared. Then, as a donor on the substrate 1 by a well-known MOCVD method (metal organic chemical vapor deposition method), a donor for the silicon and the silicon substrate 1 is formed.
A buffer layer 2 containing phosphorus that functions as an impurity is formed. That is, the silicon substrate 1 is placed in the reaction chamber of the MOCVD apparatus, and the substrate 1 is heated at about 1120 ° C. for 10 minutes to perform the heating.
Mark clean. After that, the temperature of the substrate 1 is set to 850 ° C.
And TMA (trimethylaluminum) gas to 6
3 μmol / min, TMIn (trimethylindium) gas 20 μmol / min, TMG (trimethylgallium) gas 6.2 μmol / min, ammonia 0.23 mol / min, phosphine (PH ₃ ) 0.2.
1 mol / min, 21 nmol of silane (SiH ₄ ).
The buffer layer 2 made of Al _0.7 Ga _0.2 In _0.1 N _0.2 P _0.8 containing silicon as an n-type impurity is flown at a rate of about 300 angstroms for about 15 minutes on the substrate 1.
Epitaxially grow to the thickness of the film.

Next, the substrate 1 is again heated to 1120 ° C., and then the n-type semiconductor layer 6 made of n-type GaN and the active layer 7 made of InGaN are formed by the well-known MOCVD method.
And the p-type semiconductor layer 8 made of p-type GaN are successively and sequentially laminated.

Thereafter, the anode electrode 4 and the cathode electrode 5 are formed to complete the light emitting diode.

This embodiment has the following effects. (1) The buffer layer 2 contains phosphorus that functions as a donor impurity for silicon. Therefore, Al, which functions as an acceptor impurity for silicon, diffuses from the buffer layer 2 to the silicon substrate 1 as well as phosphorus by heating for a long time during formation of the buffer layer 2 and the light-emitting functional semiconductor layer 3, and also acts as a donor. Cancellation of the acceptor action occurs,
Formation of an inversion layer on the surface of the silicon substrate 1 is prevented. Therefore, unnecessary formation of the pn junction can be prevented, the resistance value of the silicon substrate 1 can be kept small, and the power consumption and operating voltage of the light emitting diode can be reduced to a high level. (2) Since the silicon substrate 1 is used, productivity,
Excellent workability and reduced material cost. As a result,
It is possible to realize a gallium nitride-based compound semiconductor light-emitting device that is less expensive than the conventional one using a sapphire substrate. (3) Since the gallium nitride-based compound semiconductor region 3 is formed on the silicon substrate 1 with the buffer layer 2 interposed therebetween, the crystallinity of the silicon substrate 1 which is well inherited in the plane orientation of the silicon substrate 1 is obtained. A good gallium nitride-based compound semiconductor region 3 can be formed. Therefore, it is possible to obtain a gallium nitride-based compound semiconductor light emitting device having good light emitting characteristics. (4) The buffer layer 2 in which a part of N is substituted with P, As, Sb, etc. is a compound in which the group 5 compound is only N (eg AlN).
Has a smaller band gap compared to. As a result, band discontinuity between the silicon substrate 1 and the buffer layer 2 is improved.

[0024]

[Second Embodiment] Al _0.7 Ga _0.2 I of the first embodiment
Instead of the buffer layer 2 made of n _0.1 N _0.2 P _0.8 , Si
A doped AlN _0.2 P _0.8 buffer layer was formed, and other than that, a light emitting device was manufactured by the same method as in the first embodiment.
AlN _0.2 P _0.8 of this embodiment is x = 1 in the above chemical formula,
It is a compound semiconductor corresponding to y = 0 and a = 0.2. Even if the buffer layer is formed in this way, the same effect as that of the first embodiment can be obtained.

[0025]

[Modification] The present invention is not limited to the above-described embodiment, and the following modifications are possible. (1) In the embodiment, phosphorus (P) forming the buffer layer 2 functions as a donor impurity with respect to the silicon substrate 1. However, an element that does not form the compound semiconductor of the buffer layer 2 but has a function as a donor impurity for silicon can be included in the buffer layer. (2) When forming the light emitting functional semiconductor region 3, a donor impurity (for example, phosphorus) for silicon can be introduced to diffuse the donor impurity from the semiconductor region 3 side to the silicon substrate 1 through the buffer layer 2. That is, when any one or any two or all of the n-type semiconductor layer 6, the active layer 7, and the p-type semiconductor layer 8 are formed, a donor impurity for silicon is introduced and diffused into the silicon substrate 1. You can In this case, the n-type semiconductor layer 6 or the active layer 7
Alternatively, when the p-type semiconductor layer 8 contains a constituent element that can be a donor impurity of the silicon substrate 1 such as a compound semiconductor containing phosphorus (P) (for example, InGaPN), an epitaxial growth step using this constituent element as a donor impurity of silicon In, it can be diffused into the silicon substrate 1. (3) Substrate 1, buffer layer 2, light emitting functional semiconductor region 3
The conductivity type of can be reversed from the embodiment of FIG. (4) The number of gallium nitride based semiconductor layers included in the light emitting functional semiconductor region 3 can be increased or decreased. (5) The layers 6, 7, and 8 of the semiconductor region 3 are formed of GaN and Al.
NGaN, InGaN, AlInN, InGaN, Al
A nitride-based compound semiconductor such as InGaN or AlN can be used. (6) The substrate 1 is preferably single crystal silicon, but may be conductive polycrystalline silicon or a silicon compound. (7) Chemical formula showing a buffer layer 2 Al _x Ga _y In
_The P of _1-xy N _a P _1-a can be replaced with As or Sb.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a light emitting diode according to an embodiment of the present invention.

[Explanation of symbols]

1 Silicon substrate 2 AlGaInNP buffer layer 3 Light emitting semiconductor region 4 Anode electrode 5 Cathode electrode

Continued front page    (72) Inventor Masaki Yanagihara             Sanke, 3-6 Kitano, Niiza City, Saitama Prefecture             N Denki Co., Ltd. (72) Inventor Junji Sato             Sanke, 3-6 Kitano, Niiza City, Saitama Prefecture             N Denki Co., Ltd. (72) Inventor Yoshitaka Tanaka             Sanke, 3-6 Kitano, Niiza City, Saitama Prefecture             N Denki Co., Ltd. F-term (reference) 5F041 AA24 CA03 CA22 CA40 CA49                       CA57 CA65                 5F073 AA55 CA01 CB04 CB14 DA05                       EA23

Claims (3)

[Claims] 1. A semiconductor substrate of a predetermined conductivity type, which is made of silicon or a silicon compound containing a conductivity determining impurity and has a low resistivity, and a nitride compound which is disposed adjacent to one main surface of the substrate. A buffer layer made of a semiconductor and containing an element that functions as an impurity of the same conductivity type as that of the substrate with respect to the silicon semiconductor, and a plurality of buffer layers arranged adjacent to the buffer layer to obtain a light emitting function. A semiconductor region having a nitride-based compound semiconductor layer, a first electrode arranged on the front surface side of the semiconductor region, and a second electrode arranged on the other main surface side of the substrate. A semiconductor light emitting device characterized by being provided. 2. A step of preparing a semiconductor substrate of a predetermined conductivity type, which is made of silicon or a silicon compound containing a conductivity determining impurity and has a low resistivity, and a nitride-based material on one main surface of the substrate. Forming a buffer layer, which is made of a compound semiconductor and contains an element that functions as an impurity of the same conductivity type as the predetermined conductivity type of the substrate with respect to the silicon semiconductor, by a vapor phase growth method; A step of forming a semiconductor region including a plurality of nitride-based compound semiconductor layers for obtaining a light emitting function by a vapor phase epitaxy method, and forming a first electrode on the front surface side of the semiconductor region, And a step of forming a second electrode on the main surface side. 3. A step of preparing a semiconductor substrate of a predetermined conductivity type, which is made of silicon or a silicon compound containing a conductivity determining impurity and has a low resistivity, and a nitride-based material on one main surface of the substrate. A step of forming a buffer layer made of a compound semiconductor by a vapor phase epitaxy method, and a step of forming a semiconductor region including a plurality of nitride compound semiconductor layers for obtaining a light emitting function on the buffer layer by a vapor phase epitaxy method And a step of forming a first electrode on the front surface side of the semiconductor region and forming a second electrode on the other main surface side of the substrate, the method comprising: In order to obtain at least one of the plurality of nitride-based compound semiconductor layers, the atmosphere for forming at least one of the plurality of nitride-based compound semiconductor layers should include an element that functions as an impurity of the same conductivity type as the predetermined conductivity type of the substrate with respect to the silicon semiconductor. The method of manufacturing a semiconductor light emitting element characterized.