JPH088492A - Method for manufacturing II-VI compound semiconductor light emitting device - Google Patents

Abstract

(57) [Summary] [Objective] In the case of adopting a manufacturing method involving heat treatment after an epitaxial growth step, it has stable light emission characteristics, that is, has a low threshold current I _th and has a long life. It can be so. [Structure] When the lattice constants of the cladding layers 1 and 2 are a _c and the lattice constant of the active layer 3 is a, ε ₁ = | a _c
-A | / a strain according to the active layer given by _c epsilon ₁
Is set to 0 ≦ ε ₁ <1.5 [%], or the voltage drop Vi generated at the interface between the III-V group compound semiconductor and the II-VI group compound semiconductor is set to 0 ≦ Vi ≦ 1.2 [V]. As at least one of the above configurations, at least the first clad layer 1, the active layer 3, and the second clad layer 2 each made of a II-VI group compound semiconductor are epitaxially formed on the III-V group substrate 20. Process and II on the substrate 20
-200 ° C after epitaxy of the group VI compound semiconductor layer
The target II through a heating step of heating at 450 ° C.
A -VI compound semiconductor light emitting device is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a II-VI group compound semiconductor light emitting device.

[0002]

2. Description of the Related Art In, for example, magneto-optical recording for performing optical recording and / or reproduction, a semiconductor light emitting element which emits light of short wavelength such as green or blue is required as a light source for improving recording density and increasing resolution. Nature is increasing.

For this type of semiconductor light emitting device, ZnM
A semiconductor light emitting device using a gSSe-based II-VI group compound semiconductor has attracted attention. In this case, Zn is added to the active layer.
CdSe is used, and ZnMgSSe is used as a cladding layer that sandwiches the CdSe to form a heterojunction. In this case, the composition of Mg and S in the clad layer and the composition of Cd in the active layer are selected in consideration of only good confinement of carriers and light in the active layer.

In the manufacturing process of this semiconductor light emitting device, after the epitaxy of each semiconductor layer constituting the semiconductor light emitting device, for example, heating accompanying the end face coating on the emission end face of the light emission and the end face opposite thereto, or alloying of electrodes. It goes through high temperature heating such as heating for processing.

However, in the production of the II-VI group compound semiconductor light emitting device, when the above-mentioned heating step is performed after the epitaxy of each semiconductor layer, the light emitting characteristics of the semiconductor light emitting device, especially the threshold current after the heating. Come of increase. Therefore, in the II-VI group compound semiconductor light emitting device, there is a problem in finally obtaining a stable II-VI group compound semiconductor light emitting device having a low threshold current, a low operating current, and a long life.

[0006]

In the present invention, I
When a manufacturing method involving heat treatment after the epitaxial growth step is used to manufacture a group I-VI compound semiconductor light emitting device, it has stable light emission characteristics, that is, has a low threshold current I _th and has a long life. Provided is a method for manufacturing a II-VI group compound semiconductor light-emitting device which can be realized.

[0007]

According to the first aspect of the present invention, the lattice constants of the cladding layers 1 and 2 are set to a _c, and the lattice of the active layer 3 is set as shown in FIG. Constant a
When _{a, ε 1 = | a c -a} | a / strain epsilon ₁ according to the active layer given by _{a c, 0 ≦ ε 1 <} 1.5 [%]
Or the voltage drop Vi generated at the interface between the III-V group compound semiconductor and the II-VI group compound semiconductor is 0 ≦ Vi.
As a configuration of at least one of ≦ 1.2 [V], at least I on the III-V substrate 20
A first cladding layer 1 made of a group I-VI compound semiconductor;
Through the steps of epitaxy of the active layer 3 and the second cladding layer 2 and the heating step of heating 200 ° C. to 450 ° C. after the epitaxy of the II-VI group compound semiconductor layer on the substrate 20. A II-VI group compound semiconductor light emitting device is obtained.

According to a second aspect of the present invention, in the above-mentioned production method of the present invention, the heating step is a heating step accompanied by end face coating on the emission end face of light emission and the end face opposite to the emission end face.

According to a third aspect of the present invention, in the above-mentioned production method of the present invention, the heating step is a heating step at the time of alloying the electrodes.

[0010]

In the manufacturing method of the present invention, on the III-V group substrate 20,
In the case of epitaxy semiconductor layer of Group II-VI, with subsequent heat treatment, which causes a variation in the characteristics, especially the threshold current I _th of the light emitting semiconductor device, the strain epsilon ₁ according to the active layer, further III- It depends on the voltage drop Vi that occurs at the interface between each of the semiconductors of group V and group II-VI.
By specifying the respective values of the strain ε ₁ and the voltage drop Vi, the threshold current of the target light-emitting device produced through high temperature heating, particularly heating in the range of 200 ° C. to 450 ° C. It has been _{clarified that} the change ΔI _{th of} I _th can be made small to the extent that it does not cause a problem in characteristics.

[0011]

EXAMPLES Examples of the production method of the present invention will be described. In the present invention, for example, a light emitting semiconductor element such as a laser diode whose schematic cross-sectional view is shown in FIG. 1 is manufactured.
In this example, a so-called SCH (Separate Confinement Heterostructure) structure in which a guide layer is formed with an active layer sandwiched is used, but a normal DH (Double Hetero) structure without a guide layer is used. The present invention can be applied to obtain a II-VI semiconductor light emitting device having a layer and an active layer.

In this case, for example, an n-type substrate 350 of III-V made of GaAs having a thickness of 350 μm is prepared. Then, the substrate 20 is heated to, for example, about 580 ° C. to 600 ° C. to clean the surface thereof, and then the substrate 20.
Similar to this substrate 20, a III-V group GaA
Epitaxy the first buffer layer 21 with s. Then, the substrate 20 on which the first buffer layer 21 is formed
In a vacuum to a Group II-VI MBE (Molecular Beam Epitaxy) device, where on the first buffer layer 21,
The second buffer layer 11 made of ZnSe, the first cladding layer 1 made of ZnMgSSe doped with an n-type impurity, for example, Cl, and the first guide layer 11 made of ZnS _0.06 Se _0.94 .
n _1-X Cd _X Se active layer 3, ZnS _0.06 Se _0.94
Of the second guide layer 12, a second cladding layer 2 of p-type impurities such as nitrogen N-doped ZnMgSSe, a similar cap layer 4 of similar N-doped ZnSSe, and similar similar N-doped ZnSe constituting the contact layers 8, respectively. First semiconductor layer 5, ZnSe and ZnTe according to
The superlattice structure 6 formed by repeatedly laminating each thin film, and similarly the second semiconductor layer 7 made of, for example, N-doped ZnTe are sequentially grown by, for example, the MBE method.

In this epitaxy, in the composition Zn _{1 -X} Cd _X Se of the active layer 3 described above, the lattice constant of the clad layers 1 and 2 is set to a _c by selecting the amount x value of the Cd and the active layer 3. When the lattice constant of 3 is a, the strain ε ₁ applied to the active layer given by ε ₁ = | _ac −a | / _ac is given by the following (Equation 1)
To be selected.

[0014]

[Equation 1] 0 ≦ ε ₁ <1.5 [%]

Further, in the interface of the III-V group and II-VI group compound semiconductors, in the above-mentioned structure, the conduction current of 0..0 generated at the interface between the first buffer layer 21 and the second buffer layer 22 made of ZnSe in GaAs. The voltage drop Vi at 5 A / cm ² is selected as the following (Equation 2).

[0016]

## EQU2 ## Let 0 ≦ Vi ≦ 1.2 [V].

Then, an insulating layer 9 made of, for example, a polyimide resin is formed on the contact layer 8, and a p-type electrode 30 is ohmic-contacted to the second semiconductor layer 7 through the stripe-shaped opening 9a formed in the insulating layer 9 to form a stripe. The current-carrying portion is formed to form an oscillating portion corresponding to this stripe in the active layer 3. The p-side electrode 30 is, for example, Pd, P
t and Au are sequentially formed by vapor deposition or sputtering.

Then, an n-side electrode 31 is ohmicly formed on the other main surface of the substrate 20, that is, the back surface. The n-side electrode 31 is generally known to be capable of stably making a low resistance contact with the GaAs substrate 20.
Metals such as uGe, Ni, and Au are sequentially formed by, for example, vapor deposition, and are then alloyed by heating at about 400 ° C.

Further, both end faces of the active layer 3 (both end faces along the plane of FIG. 1 corresponding to both ends in the extending direction of the stripe) of the active layer 3 of the substrate in which the respective semiconductor layers are epitaxy on the substrate 20 in this way, that is, An end face coat for forming a resonator end face having a required reflectance is applied to the emission end face of the light emitting element and the end face on the opposite side. This end face coating is, for example, a multilayer film of Si and Al ₂ O ₃ which is deposited or sputtered by CVD (Chemical Vapor Dep
osition).

This end face coating is also performed under heating at 200 ° C. or higher in order to form a stable and strong coating during vapor deposition, sputtering, etc. in the deposition.

As described above, the heating step is performed after the epitaxy of each semiconductor layer, and the heating is performed at 200 ° C. to 450 ° C., preferably 200 ° C. to 400 ° C. Here, the temperature of 200 ° C. or higher means that the above-mentioned alloy and end face coating of the electrode are
Because it requires heating at 200 ° C. or higher. Also, 4
The reason why the temperature is 50 ° C. or lower, preferably 400 ° C. is that the carrier concentration can be stably set in each II-VI group semiconductor layer at a temperature lower than this.

Although the desired light emitting element is formed in this manner, in actual manufacturing, a large number of areas are formed on the wafer-shaped substrate 20, that is, a sufficiently large area as compared with the finally obtained light emitting element. A method of simultaneously forming each semiconductor layer corresponding to a light emitting element is adopted, and thereafter, each element is divided, that is, made into a chip.

By the way, recently, it is required to form this chip, that is, the light-emitting element to be finally obtained as a small and fine element. On the other hand, in the case of automating this chip by mechanization, for example, in order to favorably make the chip. It is desired that the chip be formed thin as the area of the chip is reduced.

However, in practice, the substrate 20 is mounted on or adhered to the substrate holder of the MBE apparatus when the epitaxy of each semiconductor layer formed on the substrate 20, that is, the above-described MBE is performed. For the purpose of ensuring the mechanical strength in handling, as described above, the epitaxy semiconductor layer formed to have a large thickness of, for example, 350 μm, on the other hand, the epitaxy semiconductor layer substantially constituting the light emitting device has the entire thickness. Substrate 2 with a size of 2 to 4 μm
It is much thinner than the thickness of 0.

Therefore, as described above, in order to reduce the thickness of the wafer before the chip formation in order to favorably form the chips, the substrate 20 is formed before the chip formation after the epitaxy of each semiconductor layer. A work of mechanically / chemically polishing 20 from its back surface to thin it to, for example, 100 μm is performed, and thereafter, the above-mentioned n-side electrode 31 is deposited and a heating alloy is applied to the polished surface.

The fact that the carrier concentration in each semiconductor layer can be stabilized by setting the temperature to 450 ° C. or lower, preferably 400 ° C. in the heating step after the epitaxy of each II-VI group semiconductor layer as described above will be described below. It can be confirmed by measurement. First, a measurement sample prepared by epitaxiing ClSe-doped ZnSe with MBE on a GaAs substrate was annealed (heated) at each temperature, and the electron concentration after each heating was measured by the van der Pau method. Measured. The measurement result is shown in FIG.

In FIG. 2, the white circles, white triangles, and black squares are plots of the measurement results for each sample. As is apparent from this, when the temperature exceeds 400 ° C., particularly 450 ° C., the electron concentration decreases, and in some cases, the electron concentration changes to such an extent that it exhibits p-type.

FIG. 3 shows a measurement sample prepared by epitaxy by MBE of ZnSe doped with nitrogen N, which is a p-type impurity, on a GaAs substrate, heated at each temperature, and the net carrier after each heating. C (capacity) -V
It shows the result measured by (voltage), and the white square points, the black triangle points, and the white circle points in FIG.
This is the case of measurement at z, 100 kHz, and 1 MHz. Even in this case, if the temperature exceeds 400 ° C., particularly 450 ° C., the hole concentration decreases.

FIG. 4 shows a measurement sample prepared by epitaxy of ZnTe doped with nitrogen N, which is a p-type impurity, on a GaAs substrate by MBE, and heated at each temperature to measure the hole concentration after each heating. It shows the result of measurement. Even in this case, the hole concentration decreases when the temperature exceeds 400 ° C., and actually, the hole concentration significantly decreases when the temperature exceeds 450 ° C.

Therefore, in the manufacturing method of the present invention, the heating temperature is kept at 450 ° C. or lower, preferably 400 ° C. or lower.

Further, in the present invention, it will be explained that the strain applied to the active layer 3 is set to the above-mentioned (Equation 1), whereby the change in the threshold current I _th due to the heat treatment can be reduced. .

That is, in this case, in the light emitting device having the structure shown in FIG. 1, one bar in which one row of devices is arranged is cut out from the substrate 20, and the threshold currents before the heat treatment for all the devices in this bar are cut out. measuring the average value I _th0 of I _th, measuring the average I _th1 similar threshold current I _th after heat treatment for similar bar, the difference I _th0 -I _th1 =
FIG. 5 shows the relationship between ΔI _th and the strain ε ₁ applied to the active layer. In FIG. 5, the black circles are plots of ΔI _th when the heating temperature is 200 ° C., the white circles are when the heating temperature is 250 ° C., and the black diamonds are when each heating temperature is 300 ° C. . In this case, ε ₁ is 1.2
% (The average Vi of the elements of this bar was 1.7 V), 1.3% (the average Vi of the elements of this bar was 1.
It was 2V. ), 1.45% (the average Vi of the element of this bar was 6.8 V), 1.48% (the average Vi of the element of this bar was 0.8 V), 1. 5%
(The average Vi of the elements of this bar was 1.8 V.), 1.6% (the average Vi of the elements of this bar was 1.
It was 6V. ) Is the measurement result.

According to FIG. 5, when ε ₁ exceeds 1.5%,
It can be seen that the difference ΔI _th between the threshold currents before heating and after heating becomes large.

Further, FIG. 6 shows the difference ΔI _th between the average threshold currents before and after the similar heating for a plurality of light emitting elements of one bar described above as III-V at a current of 2 mA.
The results measured in relation to the average voltage drop Vi occurring at the interface between the Group III and Group II-VI compound semiconductors are shown. In FIG. 6, black circles are plots of ΔI _th when the heating temperature is 200 ° C., white circles are when the heating temperature is 250 ° C., and black squares are each ΔI _th when the heating temperature is 300 ° C. . In this case, Vi = 0.8 [V] (the average ε ₁ of the element of this bar was 1.45%), Vi = 1.
0 [V] (the average ε ₁ of the element of this bar was 1.82%), Vi = 1.2 [V] (the average ε ₁ of the element of this bar was 1.30%. ), Vi = 1.4
[V] (the average ε ₁ of the element of this bar was 1.10%), Vi = 1.6 [V] (the average ε ₁ of the element of this bar was 1.60%) .), Vi = 1.7 [V]
(The average ε ₁ of the elements of this bar was 1.20%.).

From FIG. 5, Vi is 1.2 [V] or more, especially 1.
It can be seen that if it is 5 [V] or more, the difference ΔI _th between the threshold currents before heating and after heating becomes large.

From these facts, it is understood that ΔI _th can be kept small by specifying (Equation 1) and (Equation 2).

As described above, according to the present invention, since the increase in I _{th in} the manufacturing process can be reduced, the threshold current I _th is stably low, and thus the operating current is reduced and the life is improved. II-V that can measure
A Group I compound semiconductor light emitting device can be reliably obtained.

[0038]

As described above, according to the manufacturing method of the present invention, when the II-VI group semiconductor layer is epitaxially grown on the III-V group substrate 20, the characteristics of the light-emitting semiconductor device can be obtained by the subsequent heat treatment. In particular, the threshold current I _th fluctuates because of strain ε ₁ applied to the active layer and further III
By high temperature heating, particularly 200 ° C. or higher, by specifying at least one of the voltage drop Vi occurring at the interface between the −V group semiconductor and the II-VI group semiconductor according to the above (Equation 1) and (Equation 2).
When the desired light emitting device is manufactured through heating in the range of 450 ° C., the change ΔI in the threshold current I _th
It is possible to reduce _th to such an extent that it does not cause a problem in terms of characteristics, and further, strain ε ₁ applied to the active layer and I
By selecting both of the voltage drops Vi generated at the interface between the II-V group semiconductor and the II-VI group semiconductor as (Equation 1) and (Equation 2), the effects of both are combined, and more reliably. It is possible to stably avoid an increase in the threshold current I _th after the heat treatment, reduce the operating current, and improve the life.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an example of a II-VI compound semiconductor light emitting device obtained by the method of the present invention.

FIG. 2 is a diagram showing the heating temperature dependence of electron concentration.

FIG. 3 is a diagram showing the heating temperature dependence of the net acceptor concentration.

FIG. 4 is a diagram showing the heating temperature dependence of hole concentration.

FIG. 5 is a diagram showing measurement results of the relationship between the difference in threshold current value before and after heat treatment and the strain ε ₁ applied to the active layer.

FIG. 6 shows the difference between the threshold current values before and after the heat treatment, and II
It is a figure which shows the measurement result of the relationship with the voltage effect Vi in the interface of a IV compound semiconductor and a II-VI compound semiconductor.

[Explanation of symbols]

 1 1st clad layer 2 2nd clad layer 3 active layer 4 cap layer 5 1st semiconductor layer 6 superlattice structure 7 2nd semiconductor layer 8 contact layer 9 insulating layer 20 substrate 30 p-side electrode 31 n-side electrode

Claims (3)

[Claims] 1. When the lattice constant of the clad layer is a _c and the lattice constant of the active layer is a, ε ₁ = | _ac −a | / a
_The strain ε ₁ applied to the active layer given by _c is 0 ≦ ε
₁ <1.5 [%], or the voltage drop Vi occurring at the interface between the III-V group compound semiconductor and the II-VI group compound semiconductor is 0 ≦ Vi ≦ 1.2.
As at least one of the constitutions of [V], at least II-VI on a III-V group substrate
A first clad layer made of a group compound semiconductor, an active layer,
II-VI group, characterized by comprising: a step of epitaxying the second clad layer; and a heating step of heating at 200 ° C. to 450 ° C. after the epitaxy of the II-VI group compound semiconductor layer on the substrate. Method for manufacturing compound semiconductor light emitting device. 2. The II-VI group compound semiconductor light-emitting device according to claim 1, wherein the heating step is a heating step associated with end face coating on the emission end face of light emission and the end face opposite to the emission end face. Production method. 3. The II-V according to claim 1, wherein the heating step is a heating step when alloying the electrodes.
Method for manufacturing group I compound semiconductor light emitting device.