JP3458007B2 - Semiconductor light emitting device - Google Patents

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. More specifically, it relates to a semiconductor light emitting device using a gallium nitride based compound semiconductor suitable for blue light emission.

Here, a gallium nitride compound semiconductor is a compound of a group III element Ga and a group V element N or
A semiconductor made of a compound in which a part of Ga of the group III element is replaced with another group III element such as Al and In and / or a part of N of the group V element is replaced with another group V element such as P and As. Say.

A semiconductor light emitting device is a light emitting diode (hereinafter referred to as LED) having a double heterojunction such as a pn junction or a pin, a super luminescent diode (SLD) or a semiconductor laser diode (LD).
A semiconductor element that emits light.

[0004]

2. Description of the Related Art Conventionally, blue LEDs have a lower brightness than red and green and are difficult to put into practical use. In recent years, however, gallium nitride compound semiconductors have been used, and a low resistance p-type semiconductor layer doped with Mg has been formed. As a result, the brightness is improved and it is in the limelight.

A conventional LED using a gallium nitride based compound semiconductor has a structure as shown in FIG.

In FIG. 4, an n-type G doped with Si or the like is formed on a sapphire (Al ₂ O ₃ single crystal) substrate 21.
Low temperature buffer layer 22 made of aN, etc., also n-type G
High temperature buffer layer 23 made of aN, n-type Al _x G
a _1-x N (0 <x <1) or the like for forming a double heterojunction, an n-type cladding layer 24, undoped Ga _y
In _1-y N (0 <y <1) active layer 25, M
The p-type cladding layer 26 made of p-type Al _x Ga _1-x N or the like doped with g or the like and the cap layer 27 made of p-type GaN are formed by a metal organic compound vapor phase epitaxy method (hereinafter, MOC).
N-type clad layer 2 which is sequentially laminated by the VD method)
4, the active layer 25 and the p-type cladding layer 26 form a double heterojunction. The n-side clad layer 24 or the high temperature buffer layer 23 exposed by removing a part of the stacked semiconductor layers by etching and the cap layer 27 which is a surface layer of the stacked semiconductor layers are provided on the n-side electrode 2 respectively.
An LED is formed by providing the 9 and p-side electrodes 28.

[0007]

In the conventional semiconductor light emitting device using the gallium nitride based compound semiconductor, the Al _x Ga _1-x N layer in which the cladding layers 4 and 6 are doped with Si or Mg as described above. By using a non-doped Ga _y In _{1 -y} N layer or the like for the active layer 25 to make the band gap energy of the active layer 25 smaller than the band gap energy of the cladding layers 24 and 26 to utilize the light confinement effect. There is. By adding In to the active layer 25, the band gap energy can be reduced, and the emission wavelength is I _y in the Ga _y In _{1 -y} N layer.
The emission wavelength can be made longer as the composition ratio of n increases, but if the composition ratio of In is too large, the lattice constant is significantly different from that of GaN which is the buffer layer, and the emission efficiency is reduced. -Y) is limited to 0.2 and the emission wavelength cannot be made longer than about 480 nm.

Therefore, blue light emitting LED and green light emitting LE
490-520n with a wavelength longer than 480 nm for the purpose of D
Although light of about m is required, there is a problem that a semiconductor light emitting device having such a wavelength cannot be obtained. Further, if the composition ratio of In is increased and the emission wavelength is increased, lattice imperfections become apparent, and even if the composition ratio is 0.2, the thickness of the active layer cannot be increased and the amount of light emission cannot be increased. There is.

It is an object of the present invention to solve such a problem and to provide a semiconductor light emitting device having a wide variation range of the emission wavelength regardless of the mixed crystal ratio of In.

[0010]

A semiconductor light emitting device according to the present invention comprises a sapphire substrate on which at least an n-type cladding layer and a p-type cladding layer are sandwiched between both cladding layers, and a band is formed from a material of both cladding layers. What is claimed is: 1. A semiconductor light-emitting device comprising: a gallium nitride-based compound semiconductor layer having an active layer made of a material having a small gap energy, wherein a part of nitrogen of the gallium nitride-based compound semiconductor in the active layer is phosphorus and / or made of a compound semiconductor was replaced with arsenic, and said both cladding layers Ri do the gallium nitride based compound semiconductor containing no phosphorus and arsenic,
Mg, Zn, Cd, Be, Ca, Mn, S are added to the active layer.
selected from the group consisting of i, Se, S, Ge and Te
At least two dopants are doped, and
Two or more kinds of the same n-type or p-type dopant are added .

[0011]

[0012]

It is preferable that the active layer is a compound semiconductor in which a part of gallium of the gallium nitride compound semiconductor is replaced with In in order to elongate the emission wavelength.

[0014]

[0015]

[0016]

[0017]

[0018]

According to the semiconductor light emitting device of the present invention, in the case of a light emitting part, that is, in the case of a light emitting device having a double heterojunction, a compound in which a part of N of a gallium nitride based compound semiconductor is substituted with P and / or As in the active layer. Since it is a semiconductor, P or As is an atom whose energy band of the gallium compound is smaller than that of N, and emits light having a long wavelength. further,
Mg, Zn, Cd, Be, Ca, Mn, Si,
A few selected from the group consisting of Se, S, Ge and Te
Since it is doped with at least two kinds of dopants,
It is easy to lengthen the emission wavelength, and the same type of n-type or p-type
Since two or more dopants are added, the emission wavelength
Easy to control.

A compound semiconductor in which a part of N is replaced with P or As has a larger energy band reduction rate than a compound semiconductor in which a part of Ga is replaced with In. The lattice matching with _x Ga _1-x N or the like can be easily achieved, and the thickness of the light emitting portion (active layer) can be increased, and the amount of light emission can be increased.

Further, by adding a dopant to the active layer, different emission levels can be formed in the energy band of the crystal, so that the emission wavelength can be further lengthened. Further, the half width of the spectrum of the emission intensity with respect to the emission wavelength can be changed by the combination of the dopants. For example, when Zn and Se are added as the dopants, the emission levels of the individual dopants Zn and Se are different (Zn and S
The emission level as ZnSe is determined (not the addition of e), and the emission wavelength can be changed.

[0021]

The semiconductor light emitting device of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of a semiconductor light emitting device according to the present invention, FIG. 2 is a diagram showing the manufacturing process thereof, and FIG. 3 is a sectional view of another embodiment of the semiconductor light emitting device according to the present invention.

Example 1 In FIG. 1, reference numeral 1 is a substrate made of sapphire or the like, on which a low temperature buffer layer 2 made of n-type GaN is 0.01.
˜0.2 μm, the high temperature buffer layer 3 made of n-type GaN is about 2 to 5 μm, n-type Al _x Ga _1-x N (0 ≦ x <
The n-type cladding layer 4 made of 1) is about 0.1 to 0.3 μm, and the active layer 5 made of undoped GaN _1-u P _u (0 <u <0.2) is about 0.05 to 0.1 μm. , P-type Al
_The p-type clad layer 6 made of _x Ga _{1 -x} N is added to 0.1 to 0.
A cap layer 7 of about 3 μm and p-type GaN is sequentially laminated on the order of 0.3 to 2 μm. Si or Ge is doped to form an n-type layer, and M to form a p-type layer.
g or Zn is doped. Then, at least the cap layer 7, the p-type cladding layer 6 and the active layer 5 of the stacked compound semiconductor layers are removed by etching to expose the high temperature buffer layer 3 which is an n-type layer and the stacked outermost p layer. An n-side electrode 9 and a p-side electrode 8 are formed on the cap layer 7, which is a mold layer, respectively.

In the present invention, the compound semiconductor of the active layer 5 is Ga.
In the N _1-u P _u, not only to reduce the band gap energy than the material of the cladding layers 4 and 6, is characterized in that the part of the N in GaN _1-u P _u which was replaced with P. The ratio of P is preferably such that the value of u is 0.01 to 0.
1, more preferably 0.02 to 0.05.
If the proportion of P is too large, the emission wavelength becomes too long,
This is because the light emission from the deep level becomes large, and if it is too small, it does not reach the target wavelength.

By substituting a part of N for P, the energy band width becomes smaller and the emission wavelength can be lengthened. The emission wavelength can be made longer as the composition ratio of P is increased, but it is selected within the above range because of the lattice constant and the film quality as a crystal, and the emission wavelength is 490 to 5
It can emit light of 20 nm.

For the same reason as substituting a part of N for P, a long wavelength light emission can be obtained by substituting As for a part of N instead of P or together with P. As instead of P
When As is used, the proportion of As is selected to be 0.5 to 5 atom%, more preferably 1 to 3 atom%. This is because if the amount is too large, the emission wavelength becomes too long, and the emission from the deep level becomes large, and if it is too small, the target wavelength cannot be obtained. Further, when substituting a part of N for both elements of P and As, it is preferable that the ratios of P and As are each within the above range.

In the above-described embodiment, GaN is used as the active layer 5.
_Although the example of _1-u P _u has been described, not only partial replacement of N but also partial replacement of Ga by In to replace Ga _y In _1-y
Even a semiconductor having a composition of N _{1 -u} P _u (0 <y ≦ 1, 0 <u <0.2) has a smaller bandgap energy and a longer emission wavelength.

Furthermore, in the above-mentioned embodiment, the active layer 5 is not doped, but Mg, Zn, Cd, Be,
By doping an impurity such as Ca or Mn to form a p-type layer, or by doping an impurity such as Si, Se, S, Ge or Te to an n-type layer, the energy peculiar to the impurity is formed in the energy band gap. The emission wavelength can be lengthened because a level is created and radiative recombination occurs via this level. Among these impurities, Be, Mn, Sc, Te and the like are particularly preferable because the emission wavelength can be lengthened because a relatively deep level can be formed. Further, as impurities such as Zn and Be, Mg and Mn, Si and Te and Zn, 2
By mixing more than one kind of impurities, it contributes to long-wavelength light emission more than addition. This is because when the atomic concentration increases above a certain level, a level is created due to the interaction between the combined atoms.

Further, according to the present invention, a part of N of the gallium nitride compound semiconductor is replaced with P and / or As to achieve a longer wavelength, and the same effect as adding In can be obtained. However, since the lattice matching is made more by adding P or As than by adding In, the thickness of the active layer can be made thicker, which contributes to the increase of the luminous efficiency.

Further, in the above-mentioned embodiment, the buffer layers 2 and 3 other than the active layer 5 and the cap layer 7 are made of GaN, and the clad layers 4 and 6 are made of Al _x Ga _{1 -x} N. Other compositions may be used as long as the bandgap energy of 6 is larger than that of the active layer, and the buffer layers 2, 3 and the like may be gallium nitride-based compound semiconductors having compositions other than GaN.

Next, referring to FIG. 2, the LED of FIG.
The manufacturing method of is explained.

As shown in FIG. 2A, on a substrate 1 made of sapphire or the like, trimethylgallium (hereinafter referred to as TMG) which is an organometallic compound gas, NH ₃ and a dopant together with a carrier gas H ₂ by a MOCVD method. SiH ₄ of, GeH _4, such as to supply TeH _4, the low-temperature buffer layer 2, and 700 made of gallium nitride based semiconductor layer such as n-type GaN layer at 400 to 700 ° C.
~ 1200 ℃ high temperature buffer layer 3 0.01 ~ respectively
The growth is about 0.2 μm and about 2 to 5 μm.

Then, trimethylaluminum (hereinafter referred to as TMA) is further added to the above-mentioned gas, and the n-type cladding layer 4 containing the n-type dopants Si, Ge, Te and the like is added.
Is formed to about 0.1 to 0.3 μm.

Next, tert-butylphosphine (hereinafter referred to as TBP) is introduced in place of the above-mentioned source gas TMA, and a material having a band gap energy smaller than that of the cladding layer 4, for example, GaN _1-u P _{u is used.} The active layer 5, which is a light emitting portion, is formed to have a thickness of about 0.05 to 0.1 μm. By changing the active layer, the emission wavelength?
It became possible to change to 520 nm.

Further, the same source gas as the gas used for forming the n-type cladding layer 4 was used, and the impurity source gas was replaced with SiH ₄ to replace Mg or Zn as a p-type impurity with biscyclopentadienyl magnesium (hereinafter referred to as Cp). ₂ called Mg)
Alternatively, it is introduced into the reaction tube as dimethyl zinc (hereinafter referred to as DMZn), and the p-type cladding layer 6 of p-type Al _x Ga is formed.
Vapor growth of the _1-x N layer.

Next, to form the cap layer 7, the same gas as that for the buffer layer 3 is used as Cp ₂ as an impurity source gas.
Mg or DMZn is supplied to form a p-type GaN layer of 0.3.
Grow to a thickness of about 1 μm. The cap layer 7 is for reducing the contact resistance between the electrode and the semiconductor layer.

After that, as shown in FIG. 2B, S
A protective film 10 of iO ₂ or the like is provided on the entire surface of the growth layer of the semiconductor layer and annealed at 400 to 800 ° C. for about 20 to 60 minutes to activate the p-type cladding layer 6 and the cap layer 7.

When the annealing is completed, the temperature is lowered to room temperature and the protective film 10 is removed by wet etching.

Next, in order to form an n-side electrode, resist is applied and patterning is performed, and as shown in FIG. 2C, the surface of the gallium nitride based compound semiconductor layer from which the protective film 10 has been removed is formed. Part of the resist is removed by dry etching to expose the buffer layer 3, which is an n-type GaN layer. Then, p is formed on the surface of the laminated compound semiconductor layer.
P made of a metal film such as Au electrically connected to the mold layer
The side electrode 8 is formed by sputtering or the like on the exposed surface of the high-temperature buffer layer 3 and the n-side electrode 9 made of a metal film such as Al electrically connected to the n-type layer (FIG. 2).
(See (d)).

Next, each chip is diced to obtain LE.
A D chip is formed.

When growing the above-mentioned active layer 5, GaN _1-v
When growing As _v (0 <v <1), the above-mentioned TBP is used.
By introducing a gas of tert-butylarsine (hereinafter referred to as TBA) instead of Ga _y In _1-y N
_In the case of growing _1-u P _u (0 <y <1, 0 <u <1), by further introducing TMI into the above-mentioned raw material gas, the Ga _y In _1-y N _1-v As _v ( 0 <y <1, 0 <v
When <1) is grown, it can be obtained by introducing TMI into the source gas of GaN _1-v As _v .

When the active layer 5 is doped with an impurity, it can be obtained by further introducing an impurity source gas into the source gas for growing the active layer 5 described above.

Embodiment 2 FIG. 3 is a cross sectional view showing a second embodiment of the semiconductor light emitting device of the present invention. In this example, an LED having a homo-pn junction was used in place of the double heterojunction of Example 1, and the growth method of the gallium nitride based compound semiconductor layer and the change in composition were the same as in Example 1 described above.

In FIG. 3, a low temperature buffer layer 12 made of, for example, n-type GaN is formed on a sapphire (Al ₂ O ₃ single crystal) substrate 11 at a low temperature of 400 to 700 ° C.
It is formed to have a thickness of about 0.01 to 0.2 μm and 700 thereon.
An n-type layer 13 made of n-type GaN _1-u P _u or the like doped with Si or the like at a high temperature of up to 1200 ° C. is formed, and p-type GaN doped with Mg or the like is further formed thereon.
_The p-type layer 14 made of _1-u P _u or the like is formed to form GaN.
_A homo pn junction composed of a _1-u P _u layer is formed. p
A p-side electrode 15 made of Au, Al or the like is formed on the mold layer 14.
Is provided, and the n-side electrode 16 is provided on the n-type layer 13 exposed by etching away part of the p-type layer 14 to form a pn junction LED.

[0045] Also, instead of GaN _1-u P u in this example _{GaN 1-v As v, Ga} y In 1-y N 1-u P u, Ga
_{y In 1-y N 1-} v As v may be used a compound semiconductor layer of another composition, such as. In short, a semiconductor light emitting device that emits light with a long wavelength can be obtained by using a composition in which a part of N of the gallium nitride based semiconductor of the semiconductor layer that contributes as a light emitting layer is replaced with P and / or As.

Although the above embodiments have been described using LEDs, the present invention can be applied to various semiconductor light emitting devices such as semiconductor lasers in addition to LEDs.

[0047]

According to the semiconductor light emitting device of the present invention, a light emitting device having a wide emission wavelength can be obtained by adding P or As to the light emitting layer of the semiconductor light emitting device made of a gallium nitride based compound semiconductor. Therefore, a light emitting device with high product value can be obtained. Further, since the lattice mismatch is smaller than when In is added, the thickness of the light emitting layer can be increased, the light emission efficiency can be increased, and the brightness can be increased.

[Brief description of drawings]

FIG. 1 is an example of an LE of a semiconductor light emitting device of the present invention.
It is a section explanatory view of D.

FIG. 2 is a diagram showing a manufacturing process of the LED of FIG.

FIG. 3 shows another example L of the semiconductor light emitting device of the present invention.
It is a section explanatory view of ED.

FIG. 4 is a cross-sectional explanatory view showing an example of a conventional semiconductor light emitting device.

[Explanation of symbols] 1 substrate 4 n-type clad layer 5 Active layer 6 p-type clad layer 7 Cap layer 11 board 13 n-type layer 14 p-type layer

Continuation of the front page (56) Reference JP-A-59-171182 (JP, A) JP-A-53-117390 (JP, A) JP-A-2-275682 (JP, A) JP-A-4-236477 (JP , A) JP-A-4-192585 (JP, A) JP-A-49-134288 (JP, A) Jpn. J. Appl. Phys. Part 1, 32 [10] (1993), p. 4413-4417 (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 33/00 H01S 5/00-5/50

Claims (2)

(57) [Claims] 1. A sapphire substrate having at least an n-type clad layer and a p-type clad layer, and an active layer made of a material sandwiched between the both clad layers and having a bandgap energy smaller than that of the material of the both clad layers. A semiconductor light-emitting device comprising a stack of gallium nitride based compound semiconductor layers, wherein the active layer comprises a compound semiconductor in which a part of nitrogen of the gallium nitride based compound semiconductor is replaced with phosphorus and / or arsenic, and the two cladding layers Ri do the gallium nitride based compound semiconductor which does not include phosphorus and arsenic, Mg in the active layer, Zn, Cd, Be, Ca , Mn, S
selected from the group consisting of i, Se, S, Ge and Te
At least two dopants are doped, and
Two or more of the same type of n-type or p-type dopants are added
Ing Te semiconductor light-emitting element. 2. The semiconductor light emitting device according to claim 1, wherein the active layer is a compound semiconductor in which a part of gallium of a gallium nitride compound semiconductor is replaced with In.