JPH098409A - II-VI group semiconductor light emitting device - Google Patents

Abstract

PURPOSE: To obtain a low resistance P-type clad layer, to drop the driving voltage of an element, to extend the life of a semiconductor light emitting element and to reduce power consumption by using ZnCdMgTe as the material for a clad layer and an active layer. CONSTITUTION: In a III-VI semiconductor light emitting element of double- heterostructure or separate confinement heterostructure, Znx Cdy Mg1-x-y Te (0<=x,y,x+y<=1) is used as the material for a clad layer and a light emitting layer. At this point, the laminated structure, consisting of a light confinement layer 2, a carrier confinement layer 3, a single quantum well active layer 4, a carrier confinement layer 5 and a light confinement layer 6, is the laminated structure called isolation confinement heterostructure which is a kind of double heterostructure. Element characteristics can be improved using ZnMgTe and ZnCdTe for the P-type confinement layer 2 and the carrier confinement layer 2. The reduction in resistance of both layers 2 and 3 and the reduction of valence band discontinuation of the board 1 and the clad layer can be accomplished.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a blue-green region (wavelength 480 to 520 nm) light emitting device using a II-VI group semiconductor, ZnMgSSe has conventionally been used as a clad for carrier injection and optical confinement. However, it is difficult to add p-type impurities to this material, and even if added, the energy level of the acceptor is deep, so the hole concentration of the p-type ZnMgSSe cladding layer is about 1
The limit was × 10 ¹⁷ cm ^-3 , and as a result, the element resistance was increased.

Furthermore, since the energy level of the valence band of this material is deeper than the vacuum level by 6.7 to 6.8 eV,
It is theoretically difficult to form an ohmic electrode directly on the p-type ZnMgSSe layer. For this reason, in the element using the n-type substrate, if the electrode is directly formed on the p-type ZnMgSSe layer, the contact potential increases. In addition, because of the low hole concentration, the contact resistance with the electrode also increases.

As a result, the current-voltage (I-
In the V) characteristic, the rising voltage of the current is high and the resistance is also high. Furthermore, when a GaAs substrate that has been conventionally used as a p-type substrate is used, the valence band of the p-type cladding layer and p-type G
A large potential barrier is generated between the valence bands of the aAs substrate, and I-
The rising voltage of the V characteristic becomes high.

Due to these factors, in the present II-VI group semiconductor light emitting device, the driving voltage becomes high due to the large built-in voltage and the high differential resistance in the IV characteristic, and the life of the device is as short as about one hour. Furthermore, the power consumption for driving becomes high.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a blue-green region II-VI group semiconductor light emitting device having a long life and low power consumption.

[0007]

Means for Solving the Problems The present invention to achieve such an object is to provide a group II-VI semiconductor light emitting device having a double hetero structure or a separate confinement hetero structure with Zn _{x as} a material for the cladding layer and the light emitting layer. Cd _y M
g _1-xy Te (0 ≦ x, y, x + y ≦ 1) is used.

[0008]

Since Zn _x Cd _y Mg _1-xy Te (hereinafter referred to as ZnCdMgTe) uses Te as the VI group element, it is possible to add high-purity p-type impurities (maximum 1 × 10 ¹⁹ cm ^-3 ). It is possible. Therefore, by using these materials,
It is possible to obtain a p-type clad layer having a lower resistance than the case of using conventional ZnMgSSe.

The energy level of the valence band of these materials is 5.7 to 5.8 eV or less from the vacuum level, which is about 1 eV shallower than ZnMgSSe. Therefore, in an element used for an n-type substrate, if an electrode is directly formed on the p-type clad layer or contact layer made of these materials,
Contact potential becomes smaller than before.

Further, since the carrier concentration is also high, the contact resistance at the p-type electrode becomes smaller than in the conventional case. As a result, in the IV characteristics of the element, the rising voltage of the current is low and the element resistance is also low. Further, when a p-type substrate is used, since the energy level of the valence band of these materials is deep, the valence band of the p-type cladding layer is used. The potential barrier between the valence band of the p-type substrate is reduced, and the rising voltage of the IV characteristic is reduced.

For these reasons, the built-in voltage and the differential resistance in the IV characteristic are smaller than those in the conventional II-VI group semiconductor light emitting layer, and the driving voltage is greatly reduced. As a result, the amount of heat generated is reduced, and the life of the device can be extended. Further, power consumption for driving is also reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings.

[Embodiment 1] FIG. 1 shows a semiconductor laser according to a first embodiment of the present invention. This example uses a p-type substrate. FIG. 1 is a cross-sectional view of a laser resonator cut perpendicularly to the light propagation direction. The direction perpendicular to the paper surface is the [1-10] direction.

In the figure, 1 is p-type Zn _0.2 Cd _0.8 Te
Substrate 2 is a nitrogen-doped p-type Zn _0.04 Mg _0.96 Te optical confinement layer (thickness: 2 μm) lattice-matched to a Zn _0.2 Cd _0.8 Te substrate.
m, carrier concentration 1 × 10 ¹⁸ cm ⁻³ ), 3 is nitrogen-doped p-type Cd _0.1 Mg _0.9 Te carrier confinement layer (thickness 1 μm
m, carrier concentration 5 × 10 ¹⁷ cm ⁻³ ), 4 is thickness 10 μ
m non-doped Cd _0.36 Mg _0.64 Te single quantum well active layer, 5 is a chlorine-doped n-type Cd _0.1 Mg _0.9 Te carrier confinement layer (thickness 1 μm, carrier concentration 5 × 10 ¹⁷ c
m ^-3 ), 6 is a chlorine-doped n-type Zn _0.04 Mg _0.96 Te optical confinement layer (thickness 2 μm, carrier concentration 1 × 10 ¹⁸ c
m ^-3 ), 7 is a silicon oxide insulating layer for current constriction,
Reference numeral 8 is an n-type ohmic electrode formed by depositing titanium, platinum and gold in this order, and reference numeral 9 is a gold electrode.

Here, the optical confinement layer 2, the carrier confinement layer 3, the single quantum well active layer 4, and the carrier confinement layer 5 are included.
The layered structure including the light confinement layer 6 is a layered structure called a separate confinement hetero structure (SCH structure) which is a type of double hetero structure.
And the carrier confinement layers 3 and 5 separate and confine light and carriers.

Element characteristics When the element having the structure shown in FIG. 1 is mounted on a diamond heat sink with a junction down using a lead-tin eutectic alloy, the IV characteristics at room temperature are shown in FIG. 2 (a). .
Resonator length is 1mm, threshold current density at room temperature is 480A /
cm ² , and the oscillation wavelength is 510 nm. From FIG. 2, the current rising voltage at room temperature of the device of this example is about 4.3V.
It can be seen that it is.

As a comparative example, the characteristics of a conventional laser diode having a SCH structure similar to that of the present element, using ZnMgSSe as the cladding layer, were examined. As a result, at room temperature, the IV characteristics shown in FIG. Was obtained. The current rising voltage at room temperature is about 10.3V, which is 2V compared to this device.
More than double. The threshold current density under the same measurement conditions is 700 A / cm ^2, which is about 1.5 times that of the present device. Next, the life of the device of this example and the conventional device at room temperature was examined. The continuous operation time under a constant light output of 1 mW was measured for all the devices. The life of the device of this example was remarkably extended to 213 hours, while that of the conventional device was about 1 hour.

To improve the device characteristics, ZnMgTe and ZnCdTe are used for the p-type optical confinement layer 2 and the carrier confinement layer 3, respectively, to reduce the resistance of both layers 2 and 3 and to reduce the substrate 1 and the cladding layer 2. This is due to the reduction of the valence band discontinuity between them. Although a ZnCdTe substrate was used as the substrate 1, the present invention is not limited to this, and an HgZnTe substrate or an InGa of III-V group semiconductor is used.
An Sb substrate or the like may be used. Further, between the layer 1 and the layer 2, a nitrogen-doped p-type Z made of the same material as the substrate is used as a buffer layer.
n _0.2 Cd _0.8 Te (thickness 0.1 μm, carrier concentration 1 × 1
0 ¹⁸ cm ^-3 ) may be added.

[Embodiment 2] FIG. 3 shows a semiconductor laser according to a second embodiment of the present invention. The present embodiment uses an n-type substrate. Therefore, as shown in FIG. 3, the laser structure has a laminated structure in which pn is inverted from that when the p substrate is used.

In the figure, 10 is n-type Zn _0.2 Cd _0.8 T
e substrate, 11 is a chlorine-doped n-type Zn _0.04 Mg _0.96 Te optical confinement layer (thickness: 2 μm) lattice-matched to the Zn _0.2 Cd _0.8 Te substrate.
m, carrier concentration 1 × 10 ¹⁸ cm ⁻³ ), 12 is chlorine-doped n-type Cd _0.1 Mg _0.9 Te carrier confinement layer (thickness 1 μm
m, carrier concentration 5 × 10 ¹⁷ cm ⁻³ ), 13 is thickness 10
doped Cd _0.36 Mg _0.64 Te single quantum well active layer of [mu] m, 14 is nitrogen-doped p-type Cd _0.1 Mg _0.9 Te carrier confinement layer (thickness 1 [mu] m, carrier concentration 5 × 10 ^{1 7} c
m ^-3 ), 15 is a nitrogen-doped p-type Zn _0.04 Mg _0.96 Te optical confinement layer (thickness 2 μm, carrier concentration 1 × 10 ¹⁸ c
m ^-3 ), 16 is a silicon oxide insulating layer for current confinement, 17 is a gold electrode, 18 is an n-type ohmic electrode formed by depositing titanium, platinum and gold in this order.

Also in this embodiment, the same improvement in device characteristics as in the above-described Embodiment 1 can be obtained. This is ZnMgTe
And ZnCdTe are used for the p-type optical confinement layer 15 and the carrier confinement layer 14, respectively.
4. Reduction of resistance of 4, 15 and p-type electrode 17 and clad layer 1
This is due to the reduction of the contact resistance between No. 5 and No. 5. Although a ZnCdTe substrate was used as the substrate 10, the present invention is not limited to this, and a HgZnTe substrate or III-
An InGaSb substrate of V group semiconductor may be used. Layer 1
5 and the layer 17 are heavily doped with nitrogen p-type Zn _0.04 Mg _0.96
Te contact layer (thickness 0.05 μm, carrier concentration 1
× 10 ¹⁹ cm ^-3 ) may be added.

In the above-mentioned embodiment, ZnCdTe or ZnMgTe is used as the light confinement layer and the carrier confinement layer.
However, the same effect can be obtained by using ZnCdMgTe instead. Further, in the above embodiment,
Although the example of the laser having the separate confinement hetero structure is shown, the effect of the present invention can be obtained by using the same concept in the light emitting device having the pn junction, the double hetero structure, or these improved structures.

[0023]

As described above in detail with reference to the embodiments, the II-VI group semiconductor light emitting device of the present invention uses ZnCdMgTe as the material for the cladding layer and the active layer, and therefore has a higher resistance than the conventional ZnMgSSe. It is possible to obtain a p-type clad layer having a low Further, since the energy level of the valence band of these materials is shallower than that of conventional materials, the contact potential and contact resistance between the p-type cladding layer and the electrode or the contact resistance between the p-type cladding layer and the substrate are conventionally. It gets smaller. Due to these effects, the driving voltage of the device can be reduced, and thus the present invention has an effect that a II-VI group semiconductor laser having a long life and low power consumption can be easily obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a graph showing an example of current-voltage characteristics of the semiconductor laser of the present invention.

FIG. 3 is a sectional view of a semiconductor laser according to a second embodiment of the present invention.

[Explanation of symbols]

1 p-type Zn _0.2 Cd _0.8 Te substrate 2 nitrogen-doped p-type Zn _0.04 Mg _0.96 Te optical confinement layer 3 nitrogen-doped p-type Cd _0.1 Mg _0.9 Te carrier confinement layer 4 non-doped Cd _0.36 Mg _0.64 Te single quantum well active layer 5 chlorine Doped n-type Cd _0.1 Mg _0.9 Te carrier confinement layer 6 Chlorine-doped n-type Zn _0.04 Mg _0.96 Te optical confinement layer 7 Silicon oxide insulating layer 8 Titanium / platinum / gold electrode 9 Gold electrode 10 n-type Zn _0.2 Cd _0.8 Te substrate 11 Chlorine-doped n-type Zn _0.04 Mg _0.96 Te optical confinement layer 12 Chlorine-doped n-type Cd _0.1 Mg _0.9 Te carrier confinement layer 13 Non-doped Cd _0.36 Mg _0.64 Te single quantum well active layer 14 Nitrogen-doped p-type Cd _0.1 Mg _0.9 Te carrier confinement Layer 15 Nitrogen-doped p-type Zn _0.04 Mg _0.96 Te Optical confinement layer 16 Silicon oxide insulating layer 17 Gold electrode 18 Titanium / platinum / gold electrode

Claims (2)

[Claims] 1. Zn _z Cd _1-z Te (0 ≦ z <1), Hg _v Zn
_1-v Te (0 ≦ v ≦ 1) or In _w Ga _1-w Sb (0 ≦ w ≦
1) formed on a substrate consisting of at least Zn _x Cd _y
A II-VI group semiconductor light emitting device having a Mg _1-xy Te layer (0 ≦ x, y, x + y ≦ 1). 2. The II-VI group semiconductor light emitting device according to claim 1, wherein the Zn _x Cd _y Mg _1-xy Te layer is formed as a p-type optical confinement layer and a carrier confinement layer.