JP2663787B2 - Light emitting element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a II-VI compound semiconductor light emitting device used for a display device or the like.

[0002]

2. Description of the Related Art Recently, it has been desired to develop a blue light-emitting diode (hereinafter, referred to as an LED) having sufficient luminance and efficiency for practical use as a display light source for a wall-mounted television or the like. ZnSe or ZnS or ZnSSe which is a II-VI compound semiconductor has a band gap of 2.7 to 3.3 at room temperature.
Since it has 7 eV and has a direct transition band structure, it is expected as a semiconductor material for blue LEDs. Generally, in order to realize a blue LED with high luminance and high efficiency, it is necessary to form a pn junction structure by adding impurities to these materials to control the conduction type. However, ZnSe, ZnS or a mixed crystal ZnSSe is
It is known that both materials are difficult to obtain low resistance p-type conduction.

[0003] To date, many studies have been made on new acceptor impurities with the aim of achieving a low resistance p-type. Then, by adding N or Li into ZnSe,
There have been some reports that p-type conduction has been obtained (references: J. Nishizawa et al .; Journal of Applied Physics J. Appl. Phys. 59 (1986) 2256., AO
hki et al .; Journal of Crystal Grouse
J. Cryst. Growth 93 (1988) 692., Y. Yasuda et al .;
Applied Physics Letters Appl. Phys. Let
t. 52 (1988) 57.).

FIG. 16 shows a structure of a pn junction type blue LED obtained by adding an N impurity to ZnSe as a conventional II-VI compound semiconductor light emitting device. 201
Is an n-type GaAs substrate doped with Si; 202 is an n-type ZnSe epitaxial layer doped with Cl;
Is doped p-type ZnSe epitaxial layers, 204 and 205 are Au and AuSn electrodes, respectively.
When a forward bias is applied to the pn junction structure, electrons as minority carriers are injected from the n-type ZnSe epitaxial layer 202 into the p-type ZnSe epitaxial layer 203, and light emission is obtained.

On the other hand, as a II-VI group compound semiconductor, ZnS
There is no report that a light-emitting element using a P-type conduction of low resistance was obtained by adding such an impurity, and a pn junction type blue LED has not been obtained. .

[0006]

However, the conventional II
The ZnSe light emitting device which is a group VI compound semiconductor has the following problems.

[0007] Even if N or Li is added as an impurity to ZnSe to a conventional ZnSe light emitting device, the carrier concentration becomes p.
A practically sufficient hole concentration of 10 to 10 ¹⁶ cm ^-3 or more cannot be obtained. Therefore, sufficient blue light emission cannot be realized. Therefore, when impurities such as N and Li are added to ZnSe at a high concentration, as shown in FIG. 17, light emission from a deep acceptor level formed in a band gap of ZnSe becomes dominant in light emission characteristics, and blue light emission is obtained. There was a problem that a color could not be obtained.

Further, the structure of a conventional ZnSe light emitting device is as follows:
It has a single heterostructure of a pn junction of a p-type ZnSe layer and an n-type ZnSe layer, and is not a double heterostructure in which three or more semiconductor layers having different band gap energies are stacked. And cannot confine photons. Therefore, there is a problem that high luminous efficiency and further, stimulated emission (laser oscillation) cannot be obtained by the conventional structure.

In addition, in a light emitting device using ZnS as a II-VI compound semiconductor, even if an impurity is added, p-type conduction with low resistance is not obtained and blue light emission is not sufficient.

Accordingly, an object of the present invention is to provide a blue light emitting device having high luminance and high luminous efficiency, in which high-density carrier injection and high efficiency blue light emission can be obtained.

[0011]

Means for solving the problem are as follows. First ZnTe or ZnSTe
And a structure in which ZnS is alternately stacked, and the first ZnT
e or ZnSTe and ZnS alternately laminated
A ZnTe having the second p-conductivity type or a p-conductivity type.
Having ZnSTe and a structure in which ZnS is alternately laminated
Light emitting element. Also, ZnS having n conductivity type
A first crystal on the ZnS crystal having the n-conductivity type;
ZnTe or ZnSTe and ZnS were alternately laminated
Structure and the first ZnTe or ZnSTe and ZnS
Having a second p-conductivity type on a structure in which
ZnSTe having nTe or p conductivity type and ZnS
A light-emitting element having a structure in which the layers are alternately stacked.

[0012]

The present invention has the following effects by the above means. (1) In the case of a light emitting element using ZnS or ZnSe as a II-VI compound semiconductor, acceptor impurities are changed to ZnS or Z
Carrier concentration p-10 ¹⁶ c
A practically sufficient hole concentration of m ⁻³ or more cannot be obtained.

On the other hand, ZnTe or Z
nSTe crystals, sufficient hole concentration (p~10 ¹⁸ cm ^-3) is obtained by adding an acceptor impurity.
However, the band gaps of the p-type ZnTe crystal and the ZnSTe crystal are each near 2.26 eV,
At this size, blue light emission cannot be obtained and only green light emission can be obtained. Therefore, in order to increase the band gap from green to blue, as shown in the structure of the present invention, p-type ZnTe and undoped ZnS
Multiple quantum well structure where p is alternately stacked or p-type Zn
This is a multiple quantum well structure in which STe and non-doped ZnS are alternately stacked.

By forming the p-type layer into such a multiple quantum well structure and controlling the thicknesses of the p-type ZnTe layer and the non-doped ZnS layer of the multiple quantum well structure to predetermined sizes, the p-type multiple quantum well layer is formed. The effective bandgap of
It can be set to a desired size between the band gap 550 nm of ZnTe and the band gap 340 nm of ZnS in terms of wavelength.

Similarly, by forming the p-type layer into a p-type ZnSTe layer and a non-doped ZnS layer having a multiple quantum well structure and controlling the thicknesses of the layers to a predetermined size, the p-type multiple quantum well layer The effective band gap is calculated as Z
The desired size can be set between the band gap of eSTe of 550 nm and the band gap of ZnS of 340 nm.

Therefore, according to the present invention, a p-type layer having a practically sufficient hole concentration, a wide band gap, and a band gap large enough for blue light emission can be obtained. (2) In a multiple quantum well structure in which p-type ZnTe and non-doped ZnS are alternately stacked, or in a multiple quantum well structure in which p-type ZnSTe and non-doped ZnS are alternately stacked,
Even if a ZnTe layer and a ZnSTe layer are doped with a p-type impurity to have a sufficient p-type carrier concentration, the ZnTe layer,
Since there is no deep acceptor level in the ZnSTe layer, there is no emission other than blue emission. Therefore, a blue light-emitting element that emits strong blue light at room temperature can be obtained. (3) In a multiple quantum well structure in which ZnTe and ZnS are alternately stacked or a multiple quantum well structure in which ZnSTe and ZnS are alternately stacked, the state density has a stepwise distribution, and the state density near the band gap is obtained. Significantly increase. Therefore, high blue luminous efficiency can be obtained at room temperature. (4) By setting the structure such that the effective band gap of the first multiple quantum well structure is smaller than the effective band gap of the second multiple quantum well structure, ZnS and the first and second multiple quantum well structures are set. A double hetero structure in which three types of semiconductor layers having different band gap energies are laminated with each other can be formed. Therefore, high-density electrons and photons can be confined in the first multiple quantum well structure, which is the active region, the luminous efficiency is improved, and stimulated emission (laser oscillation) is also possible.

[0017]

(Embodiment 1) A first embodiment of the present invention will be described with reference to the drawings. FIG.
(A) is a structural sectional view of a blue light emitting device (hereinafter, referred to as an LED) of the present invention. 111 is I (indium)
A doped n-type ZnS substrate 112 is a Sb (antimony) doped ZnTe / ZnS multiple quantum well layer. The addition concentration of both I and Sb is 1 × 10 ¹⁸ cm in carrier concentration.
^-3 . Here, I is doped into the ZnS substrate 111 to make it an n-type having a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ , and the p-type uses ZnTe 112a, so that it cannot be obtained with ZnSe or ZnS and is 1 × 10 ¹⁸ cm ^{−. A} p-type having a high carrier concentration of ³ can be obtained.

Reference numerals 113 and 114 denote an Au electrode as a p-type electrode and an In electrode as an n-type electrode, respectively.

When Sb is added to the ZnTe layer 112a constituting the ZnTe / ZnS multiple quantum well layer 112, Z
The nTe layer 112a is of p-conductivity type, and holes serve as carriers. Here, ZnTe is ZnS, ZnS
This is very convenient because the p-type can be formed at a higher concentration than that of e. However, the band gap of ZnTe is 550 in wavelength conversion.
nm, and the emission color is green. Therefore, blue L
In order to achieve ED, it is necessary to increase the band gap in wavelength conversion from the current 550 nm to about 480 nm. For this purpose, the p-type layer is made of ZnTe which can be made to have a high p-type concentration, and the band gap is 340 in terms of wavelength.
The band gap of the p-type layer is increased to blue by forming a multiple quantum well structure of p-type ZnTe and non-doped ZnS using ZnS of nm.

When the carriers in the ZnTe / ZnS multiple quantum well layer 112 are confined in a potential well formed by a heterojunction, the degree of freedom is limited. As a result, the ZnTe / ZnS multiple quantum well layer 1
A quantum level is formed in 12. Since the quantum level formed in the quantum well changes depending on the thickness of the well layer, the effective band gap can be reduced from about 550 nm to 340 nm in terms of wavelength by changing the thickness of each layer of ZnTe 112 a and ZnS 112 b. it can.
In the present embodiment, the thickness of each layer of ZnTe 112a and ZnS 112b is set to 1 nm, and the effective band gap is 450 nm in terms of wavelength.

P-type ZnTe as a p-type layer and non-doped Z
The size of the band gap in the case of a multiple quantum well structure with nS can be calculated by the following equation.

[0022]

(Equation 1)

Here,

[0024]

(Equation 2)

Where k _z is the z component of the wave number vector, m _z
^{* And} m _B ^* are the electrons (holes) in the well layer and the barrier layer, respectively.
And the effective mass ΔE is the magnitude of the band offset.

Calculating from this (Equation 1), ZnTe
When the thickness of each layer of 112a and ZnS112b is 1 nm, the band gap becomes 450 nm, and the band gap of blue light emission can be controlled.

The ZnTe / ZnS multiple quantum well layer 11
2 indicates a p-conduction type, and the average hole carrier concentration is 4 × 1
0 ¹⁷ cm ^-3 was obtained. Therefore, when a positive bias is applied to the Au electrode 113 side and a negative bias is applied to the In electrode 114 side of the present invention, the n-type ZnS 111 changes from the Sb-doped ZnTe / ZnS
Electrons were injected into the region of the multiple quantum well layer 112. As a result, the electrons serving as the minority carriers are converted to Sb-doped ZnT.
Blue light emission was generated by radiative recombination with majority carriers (holes) in the e / ZnS multiple quantum well layer 112. FIG. 1B shows the light emission mechanism together with the band structure of the ZnS blue LED of the present invention.

FIG. 2 shows the current-voltage characteristics of the fabricated LED of this structure. The vertical axis is the driving current of the LED, and the horizontal axis is the driving voltage. As shown in this figure, the voltage-current characteristics show good rectification characteristics indicating the formation of a pn junction structure. Rise voltage is (Turn-on volt
age) was about 2.5 V, and the reverse bias breakdown voltage (Reverse bias breakdown) was 12 V.

The conventionally reported ZnSe pn junction LED has a very large rising voltage due to the large parasitic resistance of the ZnSe LED. However, the LED of the present structure shown in FIG. 1 has an extremely low rising voltage, and this result confirms that a good pn junction structure with low parasitic resistance is formed.

FIG. 3 also shows the current-voltage characteristics of the LED of the present invention. The vertical axis represents the forward current, and the horizontal axis represents the forward voltage. As shown in this figure, as the forward voltage applied to the LED increases, the forward current increases accordingly. In this figure, a value of n = 1.3 is obtained. Here, the n value is n represented by I = I ₀ exp (eV / nkT).

I: drive current I ₀ : constant e: elementary charge V: drive voltage n: diode ideality factor k: Boltzmann constant T: temperature In this, the n value means that the pn junction diode is in an ideal drive state It is a numerical value indicating whether or not this is the case. If n = 1, this value indicates an ideal relationship between the forward bias of the pn junction and the diffusion current. Further, when the generation and extinction of carriers due to traps in the band gap exist in the transition region of the pn junction, and the diode deviates from the ideal driving state, the value of n deviates from 1 and approaches 2. N value (Diode ideality factor) of the LED of the present invention
Has a value of n = 1.3 up to the vicinity of the forward current of 10 ⁻³ A. Therefore, it is understood that the LED of the present invention has very good pn junction characteristics. LE with this structure
By D, strong blue luminescence with a wavelength of about 460 nm was obtained at room temperature.

FIG. 4 shows the electroluminescence spectrum (Electroluminescenc) of the fabricated LED at room temperature.
(e (EL) spectrum) and photoluminescence spectrum (Photoluminescence spectrum) of the Sb-doped ZnTe / ZnS multiple quantum well layer 112 at room temperature are shown.
The forward bias voltage of the diode is 4
V. EL spectrum has a peak in a blue region of 2.7 eV. LED EL spectrum and Sb-doped Zn
Since the PL spectra of the Te / ZnS multiple quantum well layer match well, the EL emission of the LED is Sb of the LED structure.
This is considered to be due to recombination (electron-hole recombination) of holes as majority carriers and electrons as minority carriers in the doped ZnTe / ZnS multiple quantum well layer 112. The external quantum efficiency was 1%.

FIG. 5 is a characteristic diagram showing the driving current on the horizontal axis and the magnitude of blue light on the vertical axis. From this figure, it can be seen that the light emission power increases linearly with the increase in current, so that there is almost no non-radiative recombination center in the pn junction diode.

Embodiment 2 Next, an example of a method for manufacturing an LED of the present invention will be described with reference to FIG. In the present embodiment, an iodine transport method was employed as a growth method of ZnS111. First, growth by the iodine transport method will be described.

The ZnS powder is placed in high-purity hydrogen at 850 ° C.
After performing the reduction treatment for 3 hours, 2 ×
Vacuum sealing was performed at about 10 ⁻⁶ Torr, and firing was performed at 1000 ° C. for 50 hours. This was used as a raw material. A ZnS single crystal having a mirror-wrapped and chemically etched (111) plane was used as a seed crystal. The calcined ZnS and the seed crystal ZnS were sealed in a growth ampule together with iodine in an amount of 5 mg / cm ^{2 based on} the volume of the growth ampule, and growth was performed in a sealed tube. In the growth ampoule, the temperature of the baked ZnS portion was set to 850 ° C., and the temperature of the ZnS seed crystal portion was set to 840 ° C., and a temperature gradient was applied to perform growth for about 10 days.

Next, the Zn thus obtained in FIG.
Metal organic chemical vapor deposition (hereinafter referred to as MOC)
Notated as VD. ) Method to form a ZnTe / ZnS multiple quantum well structure (FIG. 6B). Dimethyl zinc and dimethyl tellurium are used as raw materials for the ZnTe layer 112a constituting the ZnTe / ZnS multiple quantum well layer 112, and the ZnS layer 11
Dimethyl zinc and hydrogen sulfide were used as raw materials for 2b.
Trimethylantimony was used as a raw material for Sb as a dopant. Dimethyl zinc, dimethyl tellurium, hydrogen sulfide,
And trimethylantimony are typically 4 × 10 ⁻⁵ mol / min and 5 to 100 × 10 ⁻⁶ m / min, respectively.
ol / min, 6 to 40 × 10 ⁻⁶ mol / min, and 6 to 30 × 10 ⁻⁶ mol / min. The substrate temperature was 350-450 ° C., and the growth pressure was 50 Torr. First, ZnS was etched with an etchant of 50% NaOH aqueous solution.
The surface oxide film of the substrate 111 is removed. Next, as shown in FIG. 6B, the Sb-doped ZnTe layer 112 is formed using dimethylzinc, dimethyltellurium and trimethylantimony.
a was 1 nm, dimethyl zinc and hydrogen sulfide were used, and the ZnS layer 112b was 1 nm, and the material gas was alternately supplied to grow 100 periods alternately. After that, FIG.
As shown in (d), the electrodes 113 and 114 were formed by metal deposition of Au and In.

FIG. 7 shows the change in the hole carrier concentration with respect to the supply flow rate of trimethylantimony. The carrier concentration of the ZnTe layer and the Sb-doped ZnTe / ZnS quantum well structure monotonically increases with the supply amount of trimethylantimony. This shows that the electric characteristics can be controlled well. Here, a high carrier concentration of 1 × 10 ¹⁷ cm ⁻³ was obtained in the Sb-doped ZnTe / ZnS quantum well structure.

Here, the ZnTe layer 112a and the ZnS layer 1
Although the film thickness of 12b is set to 1 nm, each film thickness can be changed within a range having a quantum effect and within a critical film thickness range for coherent growth. That is,
ZnTe band gap of 550 nm and ZnS340n
m, a band gap in the range between m
And the thickness of ZnS may be set.

Although the n-type ZnS substrate is used in the first and second embodiments of the present invention, an n-type ZnSe substrate or an n-type ZnSSe substrate can be similarly used. It is easily obtained by the method. Also, Z
Similar effects can be expected by using an nS substrate having an n-type ZnS layer formed as a buffer layer instead of the n-type ZnS substrate 111.

GaAs which can be obtained more easily than ZnS crystal
By using a substrate, n-type Zn formed by MOCVD on an n-type GaAs substrate instead of a ZnS crystal
By using S, n-type ZnSe or n-type ZnSSe epitaxial layers, the structure shown in the embodiment of FIG.
Can be made on a substrate.

Third Embodiment Next, a third embodiment will be described with reference to the drawings. This third
This embodiment is basically the same as the first embodiment described with reference to FIG. The difference is that GaAs 31 is used for the substrate.

In FIG. 8, reference numeral 31 denotes a Si-doped n-type Ga
As substrate, 32 is a Cl-doped n-type ZnS layer, 33 is Sb
Doped ZnTe / ZnS multiple quantum well layers, 34 and 3
5 is an Au and AuSn electrode. n-type ZnS layer 32
Is formed on a GaAs substrate 31 as a buffer layer. Therefore, it is not necessary to use the ZnS substrate 111 shown in FIG. 1, and GaAs can be used relatively easily.

The LED of this embodiment has a positive
When a negative bias is applied to the AuSn electrode 35 side, n-type Zn
Holes were injected from the S layer 32 into the region of the Sb-doped ZnTe / ZnS multiple quantum well layer 33. As a result, light emission was caused by the light-emitting recombination of the minority carriers with the majority carriers in the p-type Sb-doped ZnTe / ZnS multiple quantum well layer 33. In the voltage-current characteristics (not shown)
Rectification characteristics indicating the formation of a pn junction structure were obtained. With the LED having this structure, strong blue light emission having a wavelength of about 450 nm corresponding to light emission between quantum levels of the ZnTe / ZnS multiple quantum well layer 33 was obtained at room temperature. The external quantum efficiency was 1.2%.

Next, an example of a manufacturing process according to a fourth embodiment of the present invention will be described with reference to FIG. First, after removing the oxide film of the GaAs substrate, as shown in FIG.
Using dimethyl zinc and hydrogen sulfide as raw materials and 1-chlorooctane as a dopant raw material, the growth temperature was 3
ZnS layer 32 at a temperature of 50 to 450 ° C. and a growth pressure of 50 Torr
Grew. A typical feed of dimethylzinc, hydrogen sulfide and 1-chlorooctane is 4 × 10 ⁻⁵ each.
mol / min, 5-100 × 10 ⁻⁶ mol / min,
And 5 to 20 × 10 ⁻⁷ mol / min. As a result, the Cl concentration n of the carrier concentration n to 1 × 10 ¹⁸ cm ⁻³
Type ZnS is obtained. In addition, I, Al,
Even if Ga or the like is used, an n-type crystal can be obtained. Then successively,
ZnTe / ZnS is formed on the ZnS layer 32 by MOCVD.
A multiple quantum well structure was formed (FIG. 9C). ZnTe
/ ZnS Multiple Quantum Well Layer 33 Constituting ZnTe Layer 33
The raw materials of a are dimethylzinc and dimethyltellurium, Zn
Dimethyl zinc and hydrogen sulfide were used as raw materials for the S layer 33b. Trimethylantimony was used as a raw material for Sb as a dopant. Typical feed rates of dimethylzinc, dimethyltellurium, hydrogen sulfide, and trimethylantimony are 4 × 10 ⁻⁵ mol / min and 5-100 ×, respectively.
10 ^-6 mol / min, 6 to 40 × 10 ^-6 mol / mi
n, and 6 to 30 × 10 ⁻⁶ mol / min. The substrate temperature was 350-450 ° C., and the growth pressure was 50 Torr. As shown in FIG. 9 (c), the ZnTe layer 33a is 1 nm using dimethyl zinc and dimethyl tellurium, and the ZnS layer 33b is 1 nm using dimethyl zinc and hydrogen sulfide. Grew. Thereafter, as shown in FIG. 9D, Au and AuS
Electrodes 34 and 35 were formed by vapor deposition of n metal.

(Example 4) Further, for example, when an n-type GaAs substrate is used as described above, if a ZnSSe epitaxial layer is used instead of the n-type ZnS layer as a crystal to be formed thereon, GaAs
Lattice matching with the s-substrate 31 is possible, and quality is improved.

The present invention, as shown in FIG. 15, uses a GaAs device in which an electronic device or an optical device is formed in advance.
Is used as a substrate to enable integration of a blue LED and these electronic devices and optical devices.

In the embodiment of the present invention, a similar effect can be expected even if a ZnSTe / ZnS multiple quantum well is formed by using a p-type ZnSTe mixed crystal instead of the p-type ZnTe layer constituting the multiple quantum well layer.

(Embodiment 5) A fifth embodiment of the present invention will be described with reference to the drawings. FIG.
0 shows a structural sectional view of the ZnS blue LED. 51 is I
A doped n-type ZnS substrate, 52 is a first ZnTe / ZnS
The multiple quantum well layer 53 has a second Sb-doped ZnTe / Z
This is an nS multiple quantum well layer.

First ZnTe / ZnS multiple quantum well layer 5
2 is composed of ZnTe 52a and ZnS 52b. Here, ZnTe52a is non-doped and has a thickness of 3 nm.
The ZnS 52b is non-doped and has a thickness of 3 nm.

The second Sb-doped ZnTe / ZnS multiple quantum well layer 53 is composed of ZnTe 53a and ZnS 53b. ZnTe 53a is doped with a p-type impurity and has a thickness of 2 nm. ZnS 53b is a non-doped layer and has a thickness of 3 nm.

The structure of the LED of this embodiment is p-type ZnTe
Non-doped ZnTe / ZnS multiple quantum well layer 5 between ZnS / ZnS multiple quantum well layer 53 and n-type ZnS substrate 51
It has a double hetero structure sandwiching two.

The ZnTe / ZnS multiple quantum well layers 52 and 5
The effective bandgap of 3 is determined by the quantum level in the potential well formed by the heterojunction. Since the depth of the quantum level formed in the well depends on the thicknesses of the well layer and the barrier layer, ZnTe and Zn
By changing the thickness of each layer of S, the effective band gap can be changed from about 550 nm (corresponding to the band gap of ZnTe) to 340 nm (corresponding to the hand gap of ZnS) in terms of wavelength.

In this embodiment, the effective absorption edges of the first multiple quantum well 52 and the second multiple quantum well 53 are 4
70 nm and 440 nm. The addition concentrations of I and Sb were both set to 1 × 10 ¹⁸ cm ^{−3 in} carrier concentration. 5
4 and 55 are Au and In electrodes, respectively.

Second ZnTe / ZnS multiple quantum well layer 5
When Sb is added to the ZnTe layer 53a constituting Z3, Z
The nTe layer 53a is of a p-conductivity type, and the ZnS 53b is non-doped. However, holes function as carriers in the second ZnTe / ZnS multiple quantum well layer 53. The effective bandgap of the first multiple quantum well structure 52 is 470 nm, which is smaller than the effective bandgap of the second multiple quantum well structure 53 of 440 nm.
S and the first and second multiple quantum well structures form a double hetero structure in which three types of semiconductor layers having different band gap energies are stacked. Second ZnTe
The / ZnS multiple quantum well layer 53 showed a p-conduction type, and an average hole carrier concentration of 4 × 10 ¹⁷ cm ⁻³ was obtained.

In the present invention, the positive electrode, the In electrode 5
When a negative bias is applied to the 5th side, the second Sb-doped ZnT
e / ZnS multiple quantum well layer 53 to first ZnTe / Z
Holes are injected into the nS multiple quantum well layer 52, and electrons are similarly injected from the n-type ZnS 51 into the first ZnTe / ZnS multiple quantum well layer 52. Therefore, high-density electrons and photons can be confined in the first multiple quantum well structure 52 that is the active region. In the voltage-current characteristics, p
Rectification characteristics indicating the formation of a -n junction structure were obtained. With the LED of this structure, strong blue light with a wavelength of about 470 nm was obtained at room temperature. The external quantum efficiency was 5%.

Embodiment 6 A resonator can be formed in the LED of the present invention shown in FIG. It is shown in FIG. As shown in FIG. 11, on the second ZnTe / ZnS multiple quantum well layer 53,
SiO2 is formed, and grooves are formed in a stripe shape.

In this structure, the p-electrode Au
The holes injected from the electrodes 54 are efficiently injected into the grooves formed in the SiO2 56.

As described above, a semiconductor laser can be manufactured by forming an electrode stripe in the present laminated structure and forming a resonator (cavity) by cleaving an end face as shown in FIG.

Embodiment 7 Next, an example of a manufacturing process of the semiconductor laser shown in Embodiment 6 will be described with reference to FIG. Also in this example, the iodine transport method was adopted as a growth method of ZnS51.

First, a ZnS powder was dissolved in high-purity hydrogen for 85 days.
After reduction treatment at 0 ° C. for 3 hours, the resultant was vacuum-sealed in a quartz ampoule or the like at about 2 × 10 ⁻⁶ Torr and baked at 1000 ° C. for 50 hours. This was used as a raw material. A ZnS single crystal having a mirror-wrapped and chemically etched (111) plane was used as a seed crystal. The baked ZnS and seed crystal ZnS were sealed in a growth ampule together with iodine in an amount of 5 mg / cm ^{2 based on} the volume of the growth ampule,
Growth was performed in a sealed tube. In the growth ampoule, the temperature of the baked ZnS portion was set to 850 ° C., and the temperature of the ZnS seed crystal portion was set to 840 ° C., and a temperature gradient was applied to perform growth for about 10 days.

Next, the Z shown in FIG.
ZnTe / ZnS on the nS crystal 51 by MOCVD
Multiple quantum well structures 52 and 53 were formed (FIG. 12).
(B)). ZnTe / ZnS multiple quantum well layers 52 and 53
Dimethyl zinc and dimethyl tellurium, and ZnS layers 52b and 53b
Dimethyl zinc and hydrogen sulfide were used as raw materials. Trimethylantimony was used as a raw material for Sb as a dopant. Typical feed rates for dimethylzinc, dimethyltellurium, hydrogen sulfide, and trimethylantimony are 4 × 10 ⁻⁵ mol / min and 5-100 × 10 ⁻⁶ mol, respectively.
/ Min, 6 to 40 × 10 ⁻⁶ mol / min, and 6
３０30 × 10 ⁻⁶ mol / min. Substrate temperature is 35
The temperature was 0 to 450 ° C. and the growth pressure was 50 Torr. First, 50
% NaOH aqueous solution etchant, ZnS substrate 51
The surface oxide film is removed.

Next, as shown in FIG. 12B, the ZnTe layer 52a is
m, dimethyl zinc, and hydrogen sulfide, and the ZnS layer 52b is alternately supplied with a raw material gas of 3 nm in thickness of 3 nm.
Periodically grown. Then dimethyl zinc and dimethyl tellurium,
-Doped ZnT using AlN and trimethylantimony
The e-layer 53a was 2 nm, the ZnS layer 53b was 3 nm using dimethyl zinc and hydrogen sulfide, and the source gas was alternately supplied to grow 200 periods alternately. Then FIG.
Electrodes 54 and 55 were formed by metal deposition of Au and In as shown in (c) and (d).

Here, the ZnTe layer 52a and the ZnS layer 52
Although the film thickness of b is set to 1 nm, each film thickness can be changed within a range having a quantum effect and within a critical film thickness range for coherent growth.

In the fifth, sixth, and seventh embodiments of the present invention, the n-type ZnS substrate is used as the substrate.
An e-substrate and an n-type ZnSSe substrate can be similarly used, and these substrates can be easily obtained by an iodine transport method.

A similar effect can be expected by using a structure in which an n-type ZnS layer is formed as a buffer layer on a ZnS substrate instead of the ZnS substrate 51.

(Embodiment 8) By using a GaAs substrate which can be obtained more easily than a ZnS crystal, instead of a ZnS crystal, n-type ZnS and n-type ZnS are formed on an n-type GaAs substrate by MOCVD.
The structure shown in the embodiment of FIG. 1 can be formed on a GaAs substrate by using the Se or n-type ZnSSe epitaxial layer. Next, an eighth embodiment will be described with reference to the drawings. In FIG. 13, reference numeral 81 denotes Si-doped n-type GaAs.
A substrate, 82 a Cl-doped n-type ZnS layer, 83 a first Z
An nTe / ZnS multiple quantum well layer, 84 is a second Sb-doped ZnTe / ZnS multiple quantum well layer, and 85 and 86 are Au and AuSn electrodes.

When a positive bias is applied to the Au electrode 85 side and a negative bias is applied to the AuSn electrode 86 side of the present invention, the second Sb-doped Z
From the nTe / ZnS multiple quantum well layer 84 to the first ZnTe
Holes are injected into the / ZnS multiple quantum well layer 83, and similarly electrons are injected from the n-type ZnS 82 into the first ZnTe / ZnS multiple quantum well layer 83. Therefore, high-density electrons and photons can be confined in the first multiple quantum well structure 83 that is the active region. In the voltage-current characteristics, rectification characteristics indicating the formation of a pn junction structure were obtained. With the LED of this structure, strong blue light with a wavelength of about 470 nm was obtained at room temperature. The external quantum efficiency is 1.2
%was gotten.

Embodiment 9 Next, an example of a manufacturing process according to a ninth embodiment of the present invention will be described with reference to FIG. First, after removing the oxide film of the GaAs substrate 81, for example, as shown in FIG.
According to Method D, dimethylzinc and hydrogen sulfide are used as raw materials, and 1-chlorooctane is used as a dopant raw material.
The ZnS layer 42 was grown at 450 ° C. and a growth pressure of 50 Torr. Typical feeds of dimethylzinc, hydrogen sulfide and 1-chlorooctane are each 4 × 10 ⁻⁵ mol / mol.
min, 5 to 100 × 10 ⁻⁶ mol / min, and 5
２０20 × 10 ⁻⁷ mol / min. As a result, Cl-doped n-type ZnS having a carrier concentration of n to 1 × 10 ¹⁸ cm ⁻³ is obtained.
Is obtained. Also, an n-type crystal can be obtained by using I, Al, Ga, or the like as a dopant. Next, ZnTe / ZnS multiple quantum well structures 83 and 84 were successively formed on the ZnS layer 82 by MOCVD (FIG. 14C). Zn
Zn constituting Te / ZnS multiple quantum well layers 83 and 84
Dimethyl zinc and dimethyl tellurium were used as raw materials for the Te layers 83a and 84a, and dimethyl zinc and hydrogen sulfide were used as raw materials for the ZnS layers 83b and 84b. S as a dopant
Trimethylantimony was used as the material for b. Typical feeds of dimethylzinc, dimethyltellurium, hydrogen sulfide, and trimethylantimony are each 4 × 10 ⁻⁵ mo
1 / min, 5-100 × 10 ⁻⁶ mol / min, 6-
40 × 10 ⁻⁶ mol / min, and 6 to 30 × 10 ⁻⁶
mol / min. The substrate temperature is 350-450 ° C,
The growth pressure was 50 Torr. First, a ZnTe layer 83a of 3 nm using dimethylzinc and dimethyltellurium, and a ZnS layer 83b of 3 nm using dimethylzinc and hydrogen sulfide, were alternately supplied with a source gas to grow 50 periods alternately. Next, a 2 nm thick Sb-doped ZnTe layer 84a is formed using dimethylzinc, dimethyltellurium, and trimethylantimony, and a ZnS layer 84a is formed using dimethylzinc and hydrogen sulfide.
The b was grown alternately for 200 cycles by alternately supplying 3 nm and a source gas. Thereafter, as shown in FIG. 14D, electrodes 85 and 86 are deposited by metal deposition of Au and In.
Was formed.

Further, for example, when an n-type GaAs substrate is used as described above, ZnS is used as a crystal formed thereon.
If the Se epitaxial layer is used, lattice matching becomes possible, and the quality is improved.

As shown in FIG. 15, the present invention makes it possible to integrate a blue LED and these electronic and optical devices by using GaAs on which electronic devices and optical devices have been formed in advance as a substrate. Things.

As shown in FIG. 15, on the GaAs substrate 81, the LED 103 shown in FIG.
Field effect driving transistor and transistor (GaAs)
FET) 102 can be formed.

[0072]

According to the present invention, a p-conduction type hole injection layer can be easily obtained with good reproducibility, and high-density carrier injection and high efficiency blue light emission can be obtained according to the present invention. This has the effect. Therefore, a high-brightness, high-efficiency blue light-emitting element such as an LED or a semiconductor laser, which has never existed before, can be realized, and the industrial value is extremely high.

[Brief description of the drawings]

FIG. 1 shows a ZnS blue LED according to a first embodiment of the present invention.
Cross section and band diagram

FIG. 2 shows a ZnS blue LED according to a first embodiment of the present invention.
Figure showing current-voltage characteristics of

FIG. 3 shows a ZnS blue LED according to a first embodiment of the present invention.
Figure showing current-voltage characteristics of

FIG. 4 shows a ZnS blue LED according to a first embodiment of the present invention.
FIG. 4 shows an electroluminescence spectrum at room temperature and a photoluminescence spectrum of a Sb-doped ZnTe / ZnS multiple quantum well layer at room temperature.

FIG. 5 shows a ZnS blue LED according to a first embodiment of the present invention.
Diagram showing the relationship between the driving current of blue light and the intensity of blue light

FIG. 6 shows a ZnS blue LED according to a second embodiment of the present invention.
Manufacturing process cross section

FIG. 7 shows Sb-doped ZnTe, ZnSTe, and Zn
The figure which shows the change of the hole carrier density | concentration with respect to the supply flow rate of trimethylantimony in a Te / ZnS multiple quantum well layer.

FIG. 8 shows a ZnS blue LED according to a third embodiment of the present invention.
Cross section of the structure

FIG. 9 shows a ZnS blue LED according to a fourth embodiment of the present invention.
Manufacturing process cross section

FIG. 10 is a structural sectional view and band diagram of a blue LED according to a fifth embodiment of the present invention.

FIG. 11 is a structural diagram of a blue semiconductor laser according to a sixth embodiment of the present invention.

FIG. 12 is a sectional view showing a manufacturing process of a blue LED according to a seventh embodiment of the present invention.

FIG. 13 is a structural sectional view of a blue LED according to an eighth embodiment of the present invention.

FIG. 14 is a sectional view showing a manufacturing process of a blue LED according to a ninth embodiment of the present invention.

FIG. 15 is a structural sectional view of an integrated device of a blue LED and a GaAs device according to a tenth embodiment of the present invention.

FIG. 16 is a structural sectional view of a conventional LED using ZnSe.

FIG. 17 is a band diagram of ZnSe showing light emission through a deep level.

[Explanation of symbols]

31 GaAs substrate 32 Cl-doped n-type ZnS layer 33 Sb-doped ZnTe / ZnS multiple quantum well layer 34 Au electrode 35 AuSn electrode 51 I-doped n-type ZnS substrate 52 first ZnTe / ZnS multiple quantum well layer 53 second Sb-doped ZnTe / ZnS multiple quantum well layer 54 Au electrode 55 In electrode 81 GaAs substrate 82 Cl-doped n-type ZnS layer 83 First ZnTe / ZnS multiple quantum well layer 84 Second Sb-doped ZnTe / ZnS multiple quantum well layer 85 Au electrode 86 AuSn electrode 111 I-doped n-type ZnS substrate 112 Sb-doped ZnTe / ZnS multiple quantum well layer 113 Au electrode 114 In electrode

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-26271 (JP, A) JP-A-61-263288 (JP, A) JP-A-63-245984 (JP, A)

Claims (3)

(57) [Claims] A first ZnTe or ZnSTe;
a structure in which nS is alternately laminated; a structure in which the first ZnTe or ZnSTe is alternately laminated with ZnS;
Alternatively, a light-emitting element having a structure in which ZnSTe having p-type conductivity and ZnS are alternately stacked. 2. A ZnS crystal having an n-conductivity type and a first ZnTe crystal on the ZnS crystal having an n-conductivity type.
Or a structure in which ZnSTe and ZnS are alternately stacked; a structure in which the first ZnTe or ZnSTe and ZnS are alternately stacked; , A structure in which ZnS is alternately stacked. 3. The method according to claim 1, wherein n-type ZnSe or n-type ZnSSe crystal is used instead of the ZnS crystal.
The light-emitting element according to any one of the preceding claims.