JPH0682864B2 - Semiconductor light emitting device and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a blue semiconductor light emitting device and a method for manufacturing the same.

[Conventional technology]

In order to fabricate a highly efficient light emitting device, pn
A major requirement is that a bond can be formed. But Zn
Se can be obtained relatively easily if it has n-type conduction.
Obtaining one with p-type conduction is very difficult.
The phenomenon that only one conductivity type is obtained as described above is observed when a semiconductor having a wide band gap is used, and it is said that the phenomenon is caused by a self-compensation effect or contamination by impurities. Recently, the molecular beam epitaxy (MBE) method and the metalorganic vapor phase epitaxy (MOVPE) method, which are capable of low temperature growth under non-thermal equilibrium, have been used for the formation of ZnSe single crystal layer. However, a material having p-type conduction has not been obtained yet. In order to obtain a ZnSe single crystal film having p-type conduction, it is necessary to further reduce the donor concentration and enhance the crystallinity.

[Problems to be Solved by the Invention]

When growing a ZnSe single crystal layer using the MBE method or MOVPE method, GaAs is used as the substrate, but there are about 10 ³ dislocations / cm ² of dislocations on the GaAs substrate, and ZnSe exists on this. When the single crystal layer is grown, the dislocations in the substrate are inherited as they are. In addition, the lattice mismatch rate between ZnSe and GaAs is as large as 0.27%, which causes misfit dislocations to occur at the interface and propagate to the ZnSe layer. These dislocations form a complex defect with a doped element for controlling the conductivity type, and form a deep impurity level. In addition, gallium and arsenic diffuse from the GaAs substrate during growth to become ZnSe donor and acceptor impurities. These prevent the formation of the p-type conductive layer. In this way, the problem of dislocations and impurities hinders the conductivity type control of ZnSe, and the present invention solves each of the above problems,
The purpose is to obtain a ZnSe layer having a p-type conductive layer.

[Means for Solving the Problems]

The purpose is to grow a buffer layer on a GaAs substrate, form a ZnSe light emitting layer on the buffer layer, and
The formation of the n-type layer in the light emitting layer is achieved by doping iodine, and the formation of the p-type layer is achieved by doping nitrogen.

[Action]

In the present invention, since the buffer layer is present on the GaAs substrate,
Dislocations due to the lattice mismatch between ZnSe and GaAs do not occur at the interface. Further, dislocations existing in the GaAs substrate are absorbed by the buffer layer, and the number of dislocations propagated to the ZnSe light emitting layer is significantly reduced. Furthermore, gallium and arsenic from the GaAs substrate are also absorbed by the buffer layer and do not diffuse into the ZnSe light emitting layer.
Iodine and nitrogen are elements that replace the zinc position and the selenium position to form shallow donor and shallow acceptor levels, respectively, and are extremely stable in ZnSe. As a result, it is possible to obtain an n- and p-type conductive ZnSe light emitting layer having very good crystallinity.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional structural view showing an embodiment of a semiconductor light emitting device according to the present invention, FIG. 2 is a block diagram of a MOVPE growth apparatus in the manufacture of the above embodiment, and FIG. 3 is a ZnSe light emitting layer formed in the above embodiment. Fig. 4 is a photoluminescence characteristic diagram at 77K, and Fig. 4 is a sectional structural view showing another embodiment of the semiconductor light emitting device according to the present invention. In FIG. 1, 1 is a GaAs substrate and 2 is ZnSe.
Strained superlattice buffer layer consisting of multilayer structure with ZnS, 3 is pn
4 shows a ZnSe light emitting layer with a junction. 4 and 5 are ohmic electrodes. The ZnSe light emitting layer 3 is formed by epitaxially growing a nitrogen-doped p-type ZnSe layer 6 and an iodine-doped n-type ZnSe layer 7 on the buffer layer 2 in this order using the MOVPE method. FIG. 2 is a system diagram showing the structure of the MOVPE growth apparatus used in the above-mentioned examples. The raw material was diethyl zinc ((C ₂ H ₅ ) ₂ Zn) and ethyl iodide (C ₂ H ₅ I) for impurity doping. ) Keeps the bubbler containers 8 and 9 at predetermined temperatures, and is sent to the reaction container 17 by hydrogen whose flow rate is controlled by the gas flow rate controllers 10, 11 and 12. On the other hand, hydrogen selenide (H ₂ Se), hydrogen sulfide (H ₂ S), and ammonia (NH ₃ ) are used by diluting each gas cylinder 22,23,24 with hydrogen. Flow rate controlled by reaction vessel 17
Send to. Hydrogen is used as a carrier gas for these raw materials. 25 is a hydrogen cylinder and 13 is a gas flow controller. The GaAs substrate 1 is a substrate holder inside the reaction container 17.
It is placed on 18 and is heated to a predetermined temperature by a high frequency heating coil 19. The inside of the reaction container 17 can be kept in a reduced pressure state by an exhaust device (not shown) from the exhaust port 20.

Next, a method of manufacturing the semiconductor light emitting device shown in FIG. 1 using the apparatus shown in FIG. 2 will be described. As the buffer layer 2, a ZnSe layer and a ZnS _0.06 Se _0.94 layer were grown on the GaAs substrate 1 by 100 Å each for a total of 2000 Å. Above GaAs substrate 1
The substrate temperature was set to 300 ° C., the hydrogen gas at a flow rate of 25 cc / min, which was passed through the diethyl zinc bubbler container 8 kept at 5 ° C., was mixed and diluted with 1 liter / min of hydrogen gas, and the reaction container 17
In the case of growth of the ZnSe layer while supplying the gas through the introduction nozzle 26, the flow rate of the hydrogen selenide gas diluted with hydrogen gas was 100 cc / min, and the flow rate was 1 liter / min. After diluting, it is supplied through the introduction nozzle 26. On the other hand, in the case of ZnS _0.06 Se _0.94 layer growth, the total flow rate of hydrogen selenide and hydrogen sulfide is 100 cc / min,
The flow rate ratio of hydrogen selenide and hydrogen sulfide was set to 0.94: 0.06, and the mixture was diluted with hydrogen gas at a flow rate of 1 liter / minute, and then similarly supplied through the introduction nozzle 26. After the growth of the buffer layer 2 is completed, all the source gases are stopped,
The temperature of the substrate 1 is set to 350 ° C.

(1) p-type layer formation: 25cc / passed through a diethyl zinc bubbler container 8 at 5 ° C
A minute amount of hydrogen gas is mixed and diluted with 1 liter / minute of hydrogen gas and introduced into the reaction vessel 17. In addition, the flow rate of 100 cc / min of 5% by volume hydrogen selenide gas diluted with hydrogen gas was further increased to 1
The mixture is diluted with hydrogen gas at a flow rate of 1 / min, and then introduced into the reaction vessel 17. At the same time, purity 99.999% by volume
P-type ZnSe containing about 10 ¹⁶ nitrogen / cc of nitrogen is introduced by mixing and diluting 10 cc / min of ammonia gas with hydrogen gas at a flow rate of 100 cc / min, and then introducing it into the reaction vessel 17 and spraying it onto the GaAs substrate 1. The layer was grown at a rate of 2 μm / hour to a thickness of about 1 μm.

(2) Formation of n-type layer: 25cc / passed through a diethyl zinc bubbler container 8 at 5 ° C
Min hydrogen gas and 2cc / min hydrogen gas that has passed through an ethyl iodide bubbler container 9 at −10 ° C. are mixed and diluted with 1 liter / min hydrogen gas, and then diluted with a raw material gas and hydrogen gas. The n-type ZnSe layer containing 10 ¹⁷ to 10 ¹⁹ iodine atoms / cc was introduced by introducing the above-mentioned 5 vol% hydrogen selenide gas 100 cc / min of the raw material gas into the reaction vessel 17 and spraying it onto the GaAs substrate 1. It was grown to a thickness of approximately 2 μm at a rate of 2 μm per hour. Although the thickness of the buffer layer 2 is set to 200 nm in the embodiment, the thickness is not limited to this.
The deviation of the lattice constant between the substrate 1 and the ZnSe light emitting layer 3 is
Any value may be used as long as it has no influence on the formation of the light emitting layer 3.

The surface of the obtained ZnSe light-emitting layer 3 had a smooth mirror surface without irregularities. The full width at half maximum of the X-ray rocking curve of the ZnSe light emitting layer 3 was 80 seconds or less, which was much smaller than the value of 400 seconds when the ZnSe layer was directly grown on the GaAs substrate 1. Furthermore, the photoluminescence characteristics of the ZnSe light-emitting layer 3 are such that only blue light emission (around 462 nm) is extremely strong as shown by the curve 27 in FIG. 3, and the curve when the buffer layer 2 is not present.
Compared with 28, due to Yo emission related to dislocations and compound defects
Almost no SA emission was observed, and it was found that the crystallinity and purity were greatly improved. Also, the ohmic electrode 4
1 and 5 are provided as shown in FIG.
When the IV characteristics of the pn junction were measured, it showed good rectification characteristics, and its forward characteristics did not show hysteresis or change over time. In addition, when light was emitted at room temperature under forward bias, blue emission was dominant in the emission spectrum.

Next, another embodiment of the semiconductor light emitting device according to the present invention will be described.
As shown in the figure, this semiconductor light emitting device is formed by epitaxial growth using the MOVPE method. In FIG.
1 is a GaAs substrate, 21 is a buffer layer made of ZnS _0.03 Se _0.97 , 3 is a ZnSe light emitting layer having a pn junction, and 4 and 5 are ohmic electrodes. Buffer layer 21 provided on GaAs substrate 1
As a ZnS _0.03 Se _0.97 layer was grown to 200 nm. The temperature of the GaAs substrate 1 was set to 300 ° C., and hydrogen gas at a flow rate of 25 cc / min was passed through a diethyl zinc bubbler container kept at 5 ° C.
While mixing and diluting with hydrogen gas at a rate of 1 liter / minute, the total flow rate of hydrogen selenide and hydrogen sulfide is 100 cc / minute, while the gas is supplied into the reaction vessel 17 shown in FIG. Was mixed and diluted with hydrogen gas having a flow rate ratio of 0.97: 0.03 and a flow rate of 1 liter / minute, and then supplied through the introduction nozzle 26. The buffer layer 2
After the growth of the ZnSe, the source gas is completely stopped, the temperature of the substrate 1 is set to 350 ° C., and the ZnSe light-emitting layer 3 is formed in the same manner as in the above-mentioned embodiment.
Was formed. In FIG. 4, 6 is a nitrogen-doped p-type ZnSe layer, and 7 is an iodine-doped n-type ZnSe layer.

The surface of the obtained ZnSe light-emitting layer 3 had a smooth mirror surface without irregularities. The full width at half maximum of the X-ray rocking curve of the ZnSe light emitting layer 3 was 170 seconds or less, which was much smaller than the value of 400 seconds when the ZnSe layer was directly grown on the GaAs substrate 1. In addition, the photoluminescence property of the ZnSe light emitting layer is extremely strong only in blue light emission (around 460 nm), and Yo emission related to dislocations and SA emission due to compound defects are hardly observed compared to the case without a buffer layer, and the crystallinity is high. It was found that both the purity and the purity were greatly improved.

When the IV characteristics of the pn junction in ZnSe were measured, good rectification characteristics were shown, and its forward characteristics did not show hysteresis or change over time. Further, strong blue light emission was exhibited at room temperature under forward bias.

〔The invention's effect〕

As described above, the semiconductor light emitting device and the manufacturing method thereof according to the present invention are the semiconductor light emitting device in which the ZnSe light emitting layer is formed on the GaAs substrate via the buffer layer, and the manufacturing method thereof.
By providing a step of forming a buffer layer on the As substrate, and then forming a ZnSe light emitting layer including an n-type conductive layer doped with iodine and a p-type conductive layer doped with nitrogen on the buffer layer. , Propagation and misfit dislocation generation due to dislocations from the above-mentioned substrate are small, impurity diffusion from the above-mentioned substrate is small, and excellent in crystallinity and purity.
A ZnSe light emitting layer can be obtained. Further, by doping the above ZnSe light emitting layer with nitrogen, Zn having p-type conduction is obtained.
It is possible to obtain an Se layer, and as a result, it is possible to obtain a pn junction that has good rectifying characteristics and does not show a change over time, and that exhibits only strong blue light emission under forward bias. Therefore, the realization of a blue laser, which has been most strongly desired in the development of devices / devices in the information processing field such as an optical disk, an optical printer, and a display element, becomes promising.

[Brief description of drawings]

FIG. 1 is a sectional structural view showing an embodiment of a semiconductor light emitting device according to the present invention, and FIG. 2 is a MOVPE in the manufacture of the above embodiment.
FIG. 3 is a block diagram showing a growth apparatus, and FIG. 3 is formed in the above embodiment.
Photoluminescence characteristic diagram of ZnSe emitting layer at 77K,
FIG. 4 is a sectional structural view showing another embodiment of the semiconductor light emitting device according to the present invention. 1 ... GaAs substrate 2 ... buffer layer 3 ... ZnSe light emitting layer 6 ... nitrogen-doped p-type conduction layer 7 ... iodine-doped n-type conduction layer

Claims (4)

[Claims] 1. A semiconductor light emitting device having a ZnSe light emitting layer formed on a GaAs substrate via a buffer layer, wherein the ZnSe light emitting layer comprises an n-type conductive layer doped with iodine and a p-type conductive layer doped with nitrogen. A semiconductor light-emitting device comprising: 2. The semiconductor light emitting device according to claim 1, wherein the buffer layer has a multilayer structure of ZnSe and ZnS. 3. The semiconductor light emitting device according to claim 1, wherein the buffer layer is a solid solution of ZnSe and ZnS. 4. A method for manufacturing a semiconductor light emitting device, wherein a ZnSe light emitting layer is formed on a GaAs substrate via a buffer layer,
A step of forming a buffer layer on the GaAs substrate and then forming a ZnSe light emitting layer comprising an n-type conductive layer doped with iodine and a p-type conductive layer doped with nitrogen on the buffer layer. A method for manufacturing a semiconductor light emitting device characterized by the above.