JP2967122B2 - ZnSe 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 ZnSe semiconductor light emitting device such as a blue light emitting diode for emitting pure blue light at room temperature, which is used for a light emitting device for display.

[0002]

2. Description of the Related Art A ZnSe-based blue light-emitting device has a lower resistance than a GaP or GaAs-based green light source because a low-resistance p-type crystal cannot be obtained due to a self-compensation effect or the like and the vapor pressure of constituent elements is high. It is difficult to form a pn junction by a crystal growth method based on liquid phase growth in a thermal equilibrium state, such as a method for manufacturing a light emitting element that covers a red wavelength region. Such a ZnSe device of a blue light emitting element is formed by a vapor phase growth method such as a metal organic chemical vapor deposition method (hereinafter, referred to as a “MOCVD method”) capable of controlling conductivity by non-equilibrium low-temperature growth or molecular beam epitaxy. Hereinafter, a method of forming a MIS (Metal Insulator Semiconductor) structure or a pn junction by using, for example, "MBE") has been widely adopted.

[0003]

However, in the conventional growth method as described above, a GaAs crystal or the like having a lattice constant close to that of ZnSe is used as a substrate. Therefore, a lattice defect occurs due to lattice mismatch, or a buffer layer is added. Had to be multi-layered. Therefore, the ZnSe device manufacturing process is complicated, and there are problems to be solved such as a high production cost is required.

Further, p-type and n-type can be realized only by liquid phase growth using a Se solvent. In this case, even if either of them is post-grown, compensation of carriers at the growth interface occurs and a thick I-type is formed. Since a layer is easily formed, a new problem has arisen in that it is difficult to improve the injection efficiency even if a high carrier density is realized in one conductivity type.

An object of the present invention is to provide a ZnSe semiconductor light emitting device which has a simple device structure, has a high injection efficiency, and can emit pure blue light at room temperature. .

[0006]

In order to achieve the above object, a ZnSe semiconductor light emitting device according to the first aspect of the present invention comprises a p-type ZnSe formed by a liquid phase growth method using at least Se as a solvent main component. Growth layer and n formed on the p-type growth layer of ZnSe by metalorganic chemical vapor deposition
A p-type growth layer and an n-type layer to form a pn junction.

Further, the ZnSe according to the second aspect of the present invention.
The semiconductor light emitting device is formed by a substrate of a ZnSe p-type crystal manufactured by vapor pressure control temperature difference method using Se as a solvent main component and epitaxial growth on the substrate using vapor pressure control temperature difference method with Se as a solvent main component. A p-type growth layer, and an n ⁺ layer formed at least on the surface of the p-type growth layer as an injection layer by metal organic chemical vapor deposition, wherein a pn junction is formed by the p-type growth layer and the n ⁺ layer And

A ZnSe semiconductor light emitting device according to a third aspect of the present invention includes a ZnSe p-type growth layer formed by a liquid phase growth method using at least Se as a solvent main component, and a ZnSe semiconductor light emitting device.
Ohmic contact between an n-type diffusion layer formed on a p-type growth layer of nSe by a heat treatment diffusion method using Zn as a main component and an n ⁺ ZnSe layer formed on the surface of the n-type diffusion layer by metal organic chemical vapor deposition And a p-type growth layer and an n-type diffusion layer to form a pn junction.

In addition, the ZnSe semiconductor light emitting device according to the invention described in claim 4 is characterized in that, in addition to the above configuration, the ZnSe semiconductor light emitting device is made of ZnSe manufactured by a vapor pressure control temperature difference method using Se as a solvent main component.
A structure in which a p-type growth layer is formed on a substrate of a type crystal by epitaxial growth using Se as a solvent as a main component and a vapor pressure control temperature difference method, and a pn junction is formed by the p-type growth layer and the n-type diffusion layer. I have.

Further, the ZnSe according to the fifth aspect of the present invention.
In a semiconductor light emitting device, in a pn junction of ZnSe, at least a p-type growth layer is mainly composed of Se as a solvent main component, and a group I element Se, S compound or nitride is added as a p-type impurity, and the vapor pressure of Zn is reduced. It is configured to be formed by a vapor pressure controlled temperature difference liquid phase growth method applied onto the Se solvent.

[0011] In the ZnSe semiconductor light emitting device configured as described above, a good pn junction is formed between the ZnSe p-type growth layer and the n-type layer serving as the light-emitting layer, and the ZnSe p-type on the ZnSe substrate is formed. When a pn junction is formed between the growth layer and the n ⁺ layer, the n ⁺ layer becomes an injection layer and a contact layer. Therefore, when a forward current is applied to the ZnSe semiconductor light emitting device, majority carrier electrons are sent from the n-type layer or the n ⁺ layer to the p-type growth layer, and recombine with holes to generate light. This light is emitted to the outside. This light has a characteristic of an emission wavelength of 471 nm and a half width of 8.1 nm at room temperature,
Emit pure blue light.

Further, the ohmic contact layer lowers the contact resistance with the electrode with respect to the pn junction formed by the ZnSe p-type growth layer and the n-type diffusion layer, so that the carrier injection efficiency is high.

Further, the surface of the ZnSe p-type growth layer is formed flat, and the n-type diffusion layer is formed directly on this flat surface to reduce the crystal residual damage layer. Therefore, in the ZnSe semiconductor light emitting device of the present invention, Zn
Since the n-type layer can be formed directly on the Se p-type growth layer, there is no non-emission center due to crystal defects, and the injection efficiency is extremely large. Further, the structure of the ZnSe semiconductor light emitting device is simple p-type.
A light emitting device structure including an n-junction can be realized.

Further, the ZnSe semiconductor light emitting device of the present invention is a device having a so-called homo structure in which a heterogeneous compound such as GaAs is not used as a substrate, so that crystal defects due to lattice mismatch during crystal growth do not occur. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a cross-sectional view illustrating a configuration of a ZnSe semiconductor light emitting device manufactured according to the present invention. This ZnSe semiconductor light emitting device 10 has a pn junction device structure mainly composed of ZnSe.

In FIG. 1, a ZnSe semiconductor light emitting device 1
_{0, Na 2 S, Na 2 Se} , and p-type ZnSe substrate 1 which is prepared by adding a p-type impurity such as _{LiN 3, Na 2 S, Na} 2 Se, or the like is added LiN ₃ on the substrate -Grown p-type ZnSe growth layer 2 and n-type diffusion layer 3 formed on p-type ZnSe growth layer 2
And an n ⁺ ohmic contact layer 4 grown by MOCVD on the n-type diffusion layer 3 and a p-type ZnSe substrate 1
And a p ⁺ contact layer 5 formed on the back surface of the p ⁺ contact layer 5. A p-side electrode 6 is formed on the p ⁺ contact layer 5,
^An n-side electrode 7 having a smaller area than the p-side electrode 6 is formed on the ohmic contact layer 4. It is desirable that the n-side electrode 7 has an optimal shape for efficiently extracting light. For example, a perforated electrode corresponding to the p-side electrode 6 may be used. The p-type ZnSe growth layer 2 has a thickness of 5 to 30 μm,
Type diffusion layer 3 is 0.5 to ² μm, and n ⁺ ohmic contact layer 4 and p ⁺ ohmic contact layer 5 are 10 to 20 μm.
It is formed at about 0 °.

Next, a method for manufacturing the ZnSe semiconductor light emitting device 10 will be described. ZnSe semiconductor light emitting device 10
Is the vapor pressure control temperature difference method (hereinafter, “TDM / CVP method”)
That. ) And MOCV
It is manufactured by combining Method D. Regarding a method for obtaining a p-type bulk ZnSe single crystal, the present inventor has already proposed a vapor pressure control method, and has described a liquid phase growth method of ZnSe in which the vapor pressure of Zn is controlled by JP-B-60-37077 and JP-B-6060. -4
No. 2,199, Japanese Patent Publication No. 60-570759, Japanese Patent Publication No. 61-28640, and the like, a p-type or high-resistance substrate excellent in crystal perfection has been obtained. A method for obtaining a pn junction device by liquid phase growth using Se as a solvent main component is disclosed in Japanese Patent Publication No. 7-83139. According to this, a pn junction device having good crystallinity can be realized.

First, the p-type ZnSe substrate 1 is added with a p-type impurity such as Na ₂ S, Na ₂ Se, LiN ₃ or the like, which is a compound or nitride of a Group I element Se, S, and the like. ZnSe prepared by heat treatment growth with grain boundary growth by vapor pressure controlled temperature difference method with solvent as main component
The p-type bulk crystal was cut into a wafer at the crystal plane (111) to obtain an original substrate.

Next, on the p-type ZnSe substrate 1, the above-mentioned p-type impurity is added by using Se as a solvent as a main component.
A p-type ZnSe growth layer 2 is epitaxially grown at a growth temperature of 900 to 1100 ° C. In this case, Na ₂ S or LiN ₃ is optimal as the p-type impurity. However, this p-type epitaxial growth method is not limited to the above TDM / CVP method, but can be a slow cooling method or a dipping method.
From the point that crystals with the best crystallinity are easily obtained, TDM
It is desirable to use CVP.

Further, an n-type diffusion layer 3 is formed on the surface of the p-type ZnSe growth layer 2 using a Zn solution containing 2 to 10% of Ga. This means that, for example, about 1 g of Zn and 20 to 100 mg of Ga are introduced into a quartz ampoule having an inner diameter of 6 to 10 φ, melted and alloyed at a temperature of 600 to 800 ° C. while evacuating, and then a p-type single crystal is formed. 550 ° C.-7, sealed in vacuum while in contact with Zn solution
By performing a heat treatment at 60 ° C. for 5 to 30 minutes to diffuse Ga into the surface layer of the p-type single crystal, a carrier density of 5 × 10 5
An n-type layer region having a depth of about ¹⁶ to 1 × 10 ¹⁷ cm ⁻³ and a depth of less than 1 μm can be formed.

The n-type diffusion layer 3 has a diffusion time of about 2 hours and a diffusion temperature of 700 ° C. or higher in the conventional method, while the ZnSe semiconductor light emitting device of the present invention has a diffusion time of 5 to 3 hours.
It takes a very short time of about 0 minutes, and the diffusion temperature is 60
A low temperature of about 0 ° C. is sufficient. When grown in this way, n
It is possible to minimize the increase in the resistance of the p-layer whose type has been inverted.
However, as a result, in order to reinforce the n-layer which is slightly diluted in terms of the amount of injected carriers, as shown below, n ⁺
By growing the contact layer, the contact with the electrode is improved, and high injection efficiency can be obtained.

Next, n-type impurities such as diethyl iodine (DEI), and diethyl selenium (D
ESe), diethyl zinc (DEZn), etc.
An n ⁺ ohmic contact layer 4 is grown by OCVD. The carrier density of this n ⁺ ohmic contact layer 4 is 10 ¹⁸ cm ⁻³ or more. Since the n-layer having sufficiently high crystallinity and high carrier density can be used as an electron injection layer, the n ⁺ ohmic contact layer 4 is
Formed directly on the ZnSe type growth layer 2 to form an injection layer
^{+ It} may be a layer. By the MOCVD method, the n ⁺ ohmic contact layer 4 can reliably obtain a high carrier density at a temperature lower than the n-diffusion such that the diffusion layer 3 is not deteriorated by the heat treatment.

Next, in the same manner as the formation of the n ⁺ ohmic contact layer 4, a p ⁺ contact layer 5 of about 1 to 2 × 10 ¹⁸ cm ^{-3 is}
It is grown using Zn as a source gas and nitrogen trifluoride (NF ₃ ) as a p-type dopant.

Then, the growth substrate is taken out, and a p-side electrode 6 and an n-side electrode 7 are formed by a vacuum evaporation method using Au or an Au-based alloy (Au-Pd, Au-Pt, etc.). These metal electrodes are used as a carrier having a carrier density of 10 ¹⁶ cm ⁻³
Since a sufficient contact cannot be obtained even when formed on a type ZnSe substrate or an epitaxial layer, the n ⁺ ohmic contact layer 4 and the p ⁺ contact layer 5 are formed.

In the liquid phase epitaxial growth by the TDM / CVP method, epitaxial growth is performed on a p substrate using the above-mentioned Na ₂ S, Na ₂ Se, LiN ₃ or the like as a dopant for growing a p-type crystal.
0 ° C to 1100 ° C, Zn vapor pressure 1.7 to 13.0 atm
And the stoichiometric composition of the grown crystal is controlled.

FIG. 2 shows the relationship between the amount of impurities added and the impurity density of a p-type growth layer which is liquid phase epitaxially grown by TDM / CVP using Se as a solvent. Na
₂ Se has the highest impurity density, but Na ₂ S,
Since the morphology of the growth surface tends to be slightly uneven compared to LiN ₃ etc., a polishing / polishing step is required when an n-type layer is formed thereon, and the damaged layer due to it must be completely removed. Must.

On the other hand, when Na ₂ S and LiN ₃ are added, the growth surface smoothness is improved, so that an n-type layer can be formed directly on the growth surface, so that it is generated by the residual damage layer on the crystal surface. There is no increase in the number of non-light emitting centers due to the lattice defect. From this point, the crystal face (11
1) Regarding the deterioration of the crystallinity due to the polishing damage of the cut substrate, it is possible to expect the recovery by the melt back and the heat treatment effect at the initial stage of the p-type epitaxial growth.
11) The effect of improving the injection efficiency is greater than that of a pn junction obtained by forming an n-type layer directly on a p-type substrate.

Next, the operation of the ZnSe semiconductor light emitting device 10 will be described. FIG. 3 is a diagram showing emission wavelength characteristics when a current is applied to the ZnSe semiconductor light emitting device of the present invention in a forward direction. When a current flows in the ZnSe semiconductor light emitting device 10 in the forward direction, electrons of majority carriers are sent from the n-type diffusion layer 3 to the p-type ZnSe growth layer 2 and recombined with holes (holes) to generate light, This light is emitted to the outside. As shown in FIG. 3, at room temperature, this light has characteristics of an emission wavelength of 471 nm and a half-value width of 8.1 nm, and a pure blue light emission is realized.

As described above, in the present invention, the p-type ZnSe substrate 1 is used, and the p-type ZnSe growth layer 2 is formed by liquid phase epitaxial growth under thermal equilibrium.
Since the type ZnSe growth layer 2 has a relatively high impurity density and the crystallinity of the grown crystal is good due to the effect of controlling the vapor pressure during growth, it can be used as a light emitting layer.

In the present invention, Na ₂ is used as a dopant.
Since the p-type ZnSe growth layer is epitaxially grown using S or LiN ₃ , the surface smoothness is extremely improved, so that the n-type diffusion layer can be grown directly on the p-type ZnSe growth layer.

Therefore, the ZnS formed according to the present invention
In the e-semiconductor light emitting device, the increase in non-light emitting centers due to lattice defects caused by the residual damage layer on the crystal surface is eliminated, and the injection efficiency is extremely higher than that of a conventional device in which an n-type layer is directly formed on a p-type substrate.

[0032]

As is clear from the above description, the ZnSe semiconductor light emitting device of the present invention has an effect that the injection efficiency is good and pure blue light emission with a light emission wavelength of 471 nm and a half width of 8.1 nm can be performed at room temperature.

[Brief description of the drawings]

FIG. 1 is a sectional view of a ZnSe pn junction device structure according to the present invention.

FIG. 2 is a diagram showing the relationship between the amount of impurities added to a Se solvent and the impurity density in p-type epitaxial growth using Se as a solvent.

FIG. 3 is a diagram showing the light emission characteristics of a ZnSe pn junction device according to the present invention.

[Explanation of symbols]

Reference Signs List 1 p-type ZnSe substrate 2 p-type ZnSe growth layer 3 n-type diffusion layer 4 n ⁺ ZnSe contact layer 5 p ⁺ ZnSe contact layer 6 p-side electrode 7 n-side electrode

Claims (5)

(57) [Claims] 1. A ZnSe p-type growth layer formed by a liquid phase growth method using at least Se as a solvent main component, and an n-type layer formed on the ZnSe p-type growth layer by a metal organic chemical vapor deposition method. A ZnSe semiconductor light emitting device, comprising: a pn junction formed by the p-type growth layer and the n-type layer. 2. A vapor pressure control temperature comprising Se as a main component of a solvent.
A substrate of a ZnSe p-type crystal manufactured by the difference method;
Pressure controlled temperature difference method with Se as the main solvent on the substrate
-Type growth formed by epitaxial growth using GaN
Layer and at least a metal organic vapor phase on the surface of the p-type growth layer.
N formed as an injection layer by a growth method ⁺A p-type growth layer and the n-type growth layer.⁺Form a pn junction with the layers
And a ZnSe semiconductor light emitting device. 3. A ZnSe p-type growth layer formed by a liquid phase epitaxy method using at least Se as a solvent main component, and a heat treatment diffusion method using Zn as a solvent main component on the ZnSe p-type growth layer. an n-type diffusion layer, and n ⁺ Zn formed on the surface of the n-type diffusion layer by metal organic chemical vapor deposition.
A ZnSe semiconductor light emitting device comprising: an ohmic contact layer of a Se layer; and a pn junction formed by the p-type growth layer and the n-type diffusion layer. 4. On a substrate of a ZnSe p-type crystal manufactured by a vapor pressure control temperature difference method using Se as a solvent main component,
The p-type growth layer is formed by epitaxial growth using a vapor pressure control temperature difference method using Se as a solvent main component, and a pn junction is formed by the p-type growth layer and the n-type diffusion layer. The ZnSe semiconductor light emitting device according to claim 3. 5. In the ZnSe pn junction, at least the p-type growth layer contains Se as a solvent main component, and
5. The method according to claim 4, wherein a group element Se, S compound or nitride is added as a p-type impurity, and the Zn is formed by a vapor pressure controlled temperature difference liquid phase growth method in which a vapor pressure of Zn is applied onto the Se solvent. 4. The ZnSe semiconductor light emitting device according to 1, 2, or 3.