JPH0728052B2 - Semiconductor light emitting device and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a light emitting device using a II-VI group compound semiconductor and a method for manufacturing the same.

[Technical background of the invention and its problems]

Red to green light emitting devices using III-V compound semiconductors have entered the age of mass production and are widely used as display devices. Under such circumstances, expectations for a blue light emitting element, which is the only light emitting color lacking in the visible region, are increasing. Nevertheless, a manufacturing technique of a blue light emitting device comparable to the conventional III-V compound semiconductor light emitting device has not yet been established.

The first condition for obtaining a blue light emitting device is that the forbidden band width Eg of the semiconductor used exceeds 2.6 eV. Semiconductor crystals that satisfy this condition include ZnS (Eg = 3.5 eV) and ZnSe (Eg = 2.6 eV) which are II-VI group compound semiconductors, or mixed crystals thereof. Since these are direct transition types, high luminous efficiency is expected, and vigorous research is being conducted in various places. These II-VI group compound semiconductor single crystals are produced by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE).
Method) and the like on a III-V group compound semiconductor substrate such as GaAs or GaP. This is because the technology for mass-producing large single crystal substrates has been established for III-V compound semiconductors, but the technology for manufacturing large single crystal substrates has not yet been established for II-VI compound semiconductors. .

However, when a II-VI group compound semiconductor layer is grown on a III-V group compound semiconductor substrate, a so-called mutual diffusion phenomenon occurs in which a constituent element of one semiconductor diffuses into the other semiconductor during crystal growth, which is favorable. This was an obstacle to obtaining excellent light emission characteristics. That is, Zn, which is a group II element, has a large diffusion constant in a III-V group compound semiconductor, and forms a shallow acceptor level to act electrically. Also GaAs and Ga
G which is a group III constituent element of III-V group compound semiconductors such as P
a acts as a donor in the II-VI group compound semiconductor, and V
Group elements As and P function as acceptors. Therefore, conduction type inversion and a high resistance layer are generated near the interface between the III-V group compound semiconductor and the II-VI group compound semiconductor.

The above will be described more specifically with reference to FIG.
FIG. 5 shows an n-type GaAs substrate 51 on which n-type ZnSe is formed by MOCVD.
A light emitting device in which a layer 52 and a p-type ZnSe layer 53 are sequentially grown is shown. 55 is an n-side electrode and 55 is a p-side electrode. In such a conventional light emitting device, the n-type ZnSe layer of the n-type GaAs substrate 51 is used.
A p-type inversion layer 56 is formed at the interface with 52. This is because mutual diffusion of constituent elements occurs under high temperature conditions during crystal growth, and Zn has a large diffusion constant in GaAs and forms a shallow acceptor level. That is, when the concentration of Zn diffused in the GaAs substrate 51 exceeds the sum of the concentration of Se serving as a donor impurity in the n-type GaAs substrate 51 and the concentration of donor impurities existing in advance, the p-type inversion layer 56 is formed. .

When the p-type inversion layer 56 is formed in this manner, this light emitting element has a pnpn laminated structure. Therefore, even if a bias is applied such that the p-side electrode 55 is positive and the n-side electrode 54 is negative, the n-type ZnSe is
Since a reverse bias is applied between the layer 52 and the p-type inversion layer 56, a sufficient current cannot flow in the junction between the p-type ZnSe layer 53 and the n-type ZnSe layer 52, which is the light emitting portion.

[Object of the Invention]

The present invention has been made in view of the above points, and an inversion layer and a high resistance layer are not generated at the interface between the III-V group compound semiconductor and the II-VI group compound semiconductor, and therefore good current-voltage characteristics can be obtained. An object of the present invention is to provide a semiconductor light emitting device capable of obtaining high luminous efficiency and a method for manufacturing the same.

[Outline of Invention]

A light emitting device according to the present invention is provided with a p-type II-VI compound semiconductor layer and an n-type III-V compound semiconductor layer directly on a p-type III-V compound semiconductor substrate or via a p-type III-V compound semiconductor layer. It is characterized in that the II-VI group compound semiconductor layers are sequentially laminated and formed.

The present invention also grows and forms a p-type II-VI group compound semiconductor layer directly on a p-type III-V group compound semiconductor substrate or through a p-type III-V group compound semiconductor layer. An n-type II-VI group compound semiconductor layer is grown and formed on this to manufacture a light emitting device.

〔The invention's effect〕

According to the present invention, even if mutual diffusion of the constituent elements occurs between the III-V group compound semiconductor and the II-VI group compound semiconductor, both sides of this junction are p-type and The group II constituent element of the compound semiconductor layer serves as an acceptor in the group III-V compound semiconductor layer, and is a V of the group III-V compound semiconductor.
Since the group-constituting element serves as an acceptor in the II-VI group compound semiconductor layer, a conduction type inversion layer or a high resistance layer is not formed at this interface. II-VI formed on the p-type III-V compound semiconductor substrate as p-type impurities
If the group II constituent element of the group compound semiconductor layer is used and the group V constituent element of the III-V group compound semiconductor substrate is used as the p-type impurity of the p-type II-VI compound semiconductor layer, the mutual composition of the constituent elements during growth can be improved. Diffusion is suppressed more effectively. Therefore, a favorable current-voltage characteristic can be obtained, and a light emitting element having high luminous efficiency can be obtained.

Further, according to the method of the present invention, a III-V group compound semiconductor substrate such as GaAs, GaP or the like, for which a mass production technique for a large crystal substrate is established, is used without forming an unnecessary inversion layer or a high resistance layer. It is possible to form a pn junction with a group-VI compound semiconductor, and mass-produce a highly efficient blue light-emitting device using a group II-VI compound semiconductor such as ZnS and ZnSe.

Example of Invention

 Examples of the present invention will be described below.

FIG. 1 shows a blue light emitting device of one embodiment. In the figure,
11 is a p-type GaAs substrate, on which a 5 μm thick p-type Zn substrate is formed.
An Se layer 12 and an n-type ZnSe layer 13 having a thickness of 5 μm are sequentially laminated. The main p-type impurity of the GaAs substrate 11 is Zn, which is a Group II constituent element of ZnSe, and its concentration is, for example, 1 × 10 ¹⁸ / c.
m is ^3. The main p-type disordered material of the p-type ZnSe layer 12 is As which is a group V constituent element of GaAs, and the main n-type impurity of the n-type ZnSe layer 13 is Al. An AuZn electrode 14 is formed as a p-side electrode on the back surface of the GaAs substrate 11, and an InGa electrode 15 is formed as an n-side electrode on the surface of the n-type ZnSe layer 13.

2 (a) to (c) show the manufacturing process of this light emitting device. First, the p-type ZnSe layer 12 is grown on the Zn-doped p-type GaAs substrate 11 by the MOCVD method. Dimethyl zinc (DMZn) and dimethyl selenium (DMSe) are used as source gases, and arsine (AsH ₃ ) is used as a p-type impurity source. The crystal growth conditions are as follows: [DMSe] / [DMZn] = 2, the ratio of the molar supply amount [DMZn] of the Group II raw material to the molar supply amount [DMSe] of the Group VI raw material at 500 ° C. and 1 atm. Done in. Growth rate is about 500Å
/ min, and the p-type ZnSe layer 12 having a thickness of 5 μm under these conditions
Are formed (a). Next, the impurity raw material is changed, and the n-type ZnSe layer 13 having a thickness of 5 μm is grown under the same conditions as above (b). Triethylaluminum (TEAl) is used as the n-type impurity raw material. Finally, the AuZn electrode 14 is formed on the back surface of the GaAs substrate 11, and the InGa electrode 15 is formed on the surface of the n-type ZnSe layer 13 to complete the light emitting device (c).

It was confirmed that the light emitting device thus obtained showed a normal pn junction current-voltage characteristic, and that an inversion layer or the like did not occur at the interface between the GaAs substrate and the ZnSe layer. Further, this light emitting device exhibited good blue light emission.

FIG. 3 shows a light emitting device of another embodiment. In this embodiment, the p-type GaAs layer 32 is used as a buffer layer on the p-type GaAs substrate 31.
Is grown, and a p-type ZnSe layer 33 and an n-type ZnSe layer 34 are sequentially grown on this. Reference numeral 35 is an AuZn electrode and 36 is an InGa electrode.

The GaAs layer 32 as a buffer layer is grown by the MOCVD method using trimethyl gallium (TMG) and arsine (AsH ₃ ) as source gases and dimethylzinc (DMZn) as a p-type impurity source. The growth conditions were 700 ° C. and 1 atm, and the molar supply amount [TMG] of the group III raw material and the molar supply amount [AsH ₃ ] of the group V raw material were [AsH ₃ ] / [TMG] = 20. Keep it. The growth method of the p-type ZnSe layer 33 and the n-type ZnSe layer 34 is the same as in the previous embodiment.

Also in this example, an element having excellent light emitting characteristics was obtained as in the previous example.

Although ZnSe is used as the II-VI group compound semiconductor in the above, ZnS having a similarly wide band gap can also be used. In particular, if ZnSxSe _1- x, which is a mixed crystal of these, is used, it is possible to form a suitable heterojunction inside the device by varying the composition ratio thereof and obtain a device with higher luminous efficiency.

FIG. 4 shows a light emitting device of such an embodiment. In this embodiment, a 5 μm thick p-type ZnS _0.1 Se _0.9 layer is formed on the p-type GaAs substrate 41.
Layer 42, 1 μm thick p-type ZnSe layer 43, 5 μm thick n-type ZnSe
An S _0.1 Se _0.9 layer 44 is sequentially formed. Crystal growth is performed by the MOCVD method under the same conditions as in the previous embodiment. At that time, diethyl sulfur (DES) is used as a raw material of S. AuZn electrode 45 and InGa as p-type electrode and n-side electrode, respectively
The electrode 46 is formed.

In this device structure, the band gap of the p-type ZnSe layer 43 is 2.7e.
V, and the forbidden band width of the ZnSSe layers 42 and 44 sandwiching this is 2.8 eV. Therefore, electrons and holes are effectively confined in the p-type ZnSe layer 43 by the potential barrier caused by the difference in the forbidden band width between them, and efficient radiative recombination occurs.
Therefore, this light emitting device exhibits favorable current-voltage characteristics and highly efficient blue light emission. It is also effective to make the n-type layer portion similarly have a laminated structure of ZnS and ZnSSe.

The present invention is not limited to the above embodiments. For example, as the II-VI group compound semiconductor layer, it is mentioned in the above-mentioned embodiment.
In addition to the ZnSxSe _1- x system, ZnTe, CdS, CdSe, HgTe, etc., or a mixed crystal system thereof can be used. In addition to GaAs, GaP, InP or the like can be used as the III-V compound semiconductor substrate. The growth method of the II-VI group compound semiconductor layer is not limited to the MOCVD method, and other vapor phase growth method, MBE method, or liquid phase growth method can be used.

Besides, the present invention can be variously modified and implemented without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a diagram showing a light emitting device of one embodiment of the present invention, FIGS. 2 (a) to 2 (c) are diagrams for explaining the manufacturing process thereof, and FIGS. 3 and 4 are other embodiments. And FIG. 5 is a view showing a conventional light emitting element. 11,31,41 …… p-type GaAs substrate, 32 …… p-type GaAs layer, 12,33,
43 ... p-type ZnSe layer, 13,34, ... n-type ZnSe layer, 42 ... p-type
ZnSSe layer, 44 ... n-type ZnSSe layer, 14,35,45 ... AuZn electrode,
15,36,46 …… InGa electrode.

Claims (11)

[Claims] 1. A p-type III-V group compound semiconductor substrate, either directly or through a p-type III-V group compound semiconductor layer,
1. A semiconductor light emitting device comprising a p-type II-VI group compound semiconductor layer and an n-type II-VI group compound semiconductor layer, which are sequentially stacked. 2. A main acceptor impurity of the p-type III-V group compound semiconductor substrate or the p-type III-V group compound semiconductor layer on the p-type III-V compound semiconductor substrate is in contact with the p-type II-VI group compound semiconductor. The semiconductor light emitting device according to claim 1, wherein the layer is a Group II element. 3. A main acceptor impurity of the p-type II-VI group compound semiconductor layer is the p-type III-type compound which is in contact with the main acceptor impurity.
The semiconductor light emitting device according to claim 1, which is a group V element of a group V compound semiconductor substrate or a group III-V compound semiconductor layer formed thereon. 4. The p-type III-V compound semiconductor substrate or the p-type III-V compound semiconductor layer thereon is GaAs, and the p-type II-VI compound semiconductor layer and the n-type compound semiconductor layer.
The semiconductor light emitting device according to claim ₁ , wherein the II-VI group compound semiconductor layer is ZnSxSe _1- x (0 ≦ x ≦ 1). 5. The p-type II-VI group compound semiconductor layer is ZnSS.
The semiconductor light emitting device according to claim 1, which has a laminated structure of an e layer and a ZnSe layer, and wherein the n-type II-VI group compound semiconductor layer is ZnSSe. 6. A p-type II-VI group compound semiconductor layer and an n-type II group II-VI compound semiconductor layer directly or after growing a p-type III-V group compound semiconductor layer on a p-type III-V group compound semiconductor substrate.
A method for manufacturing a semiconductor light emitting device, which comprises sequentially forming a group VI compound semiconductor layer. 7. The main acceptor impurity of the p-type III-V group compound semiconductor substrate or the p-type III-V group compound semiconductor layer thereon is the p-type II-VI group compound semiconductor in contact therewith. The method for manufacturing a semiconductor light emitting device according to claim 6, wherein the layer is a Group II element. 8. The main acceptor impurity of the p-type II-VI group compound semiconductor layer is the p-type III-type compound which is in contact with the main acceptor impurity.
7. The method for producing a semiconductor light emitting device according to claim 6, wherein the compound is a V group compound semiconductor substrate or a V group element of a III-V group compound semiconductor layer thereon. 9. The p-type III-V compound semiconductor substrate or the p-type III-V compound semiconductor layer thereon is GaAs, and the p-type II-VI compound semiconductor layer and the n-type
The method for producing a semiconductor light emitting device according to claim 6, wherein the II-VI group compound semiconductor layer is ZnSxSe _1- x (0 ≦ x ≦ 1). 10. The p-type II-VI group compound semiconductor layer is Zn.
The n-type II-VI group compound semiconductor layer is Z
7. The method for manufacturing a semiconductor light emitting device according to claim 6, which has a laminated structure of nSe and ZnSSe. 11. The method for producing a semiconductor light emitting device according to claim 6, wherein the p-type II-VI group compound semiconductor layer and the n-type II-VI group compound semiconductor layer are grown and formed by a MOCVD method.