JPH04120775A - Tunnel junction light emitting element - Google Patents

Abstract

PURPOSE:To grow a light emitting layer having a small number of defects and to raise a light irradiating output to a practical level by composing semiconductor layers to be laminated on a substrate of semiconductors having near lattice constants. CONSTITUTION:A p-type GaAs layer is grown on a p-type GaAs substrate 6, and a ZnSe thin film 5 having wide forbidden band width and high resistance is grown thereon. Then, an i-type GaAlAs layer 4 to become a light emitting layer is grown, and a mixed crystal ratio profile is formed of an epitaxial layer. A ZnSe thin film 3 having wider forbidden band width is grown on the layer 4. The semiconductor material of a light emitting element is formed of GaAs, GaAlAs, ZnSe because the lattice constants of the semiconductors have very near values. Thus, the layer 4 to become the light emitting layer can be grown as the epitaxial layer having small number of defects.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a tunnel junction light emitting device that utilizes the tunnel effect, particularly a tunnel junction light emitting device that can control the emission peak wavelength by voltage, with improved light output. .

[Prior Art] Generally, a light emitting diode (L) is used as a solid state light emitting device.
ED), semiconductor lasers (LD), electroluminescent (EL) elements, etc. are used. However, although these devices can change the emission output by changing the applied voltage, the emission wavelength varies slightly depending on temperature fluctuations and current density.
It cannot be changed.

If a light-emitting element can be developed that can greatly control the emission peak wavelength by changing the applied voltage, it is expected to find applications in a variety of fields including the sensor field.

Recently, tunnel junction light emitting devices have been attracting attention as a potential wavelength tunable light emitting device. As shown in Figure 3, a tunnel junction light emitting device is made of metal/insulator/
It is made of metal, and when a voltage is applied to this element, electrons 31 pass through a thin insulator due to the tunnel effect, and at this time, light 32 is emitted from the junction surface.

This tunnel junction light emitting device is attracting attention as a potential wavelength tunable light emitting device because it has been reported that the short wavelength cutoff of the light emitted from it depends on the applied voltage. (Reference J, Lambe
and S, McCarthy: Phys, Rev.

Lett 37 (1976) 923), however, this device has a low light emitting output and is difficult to put into practical use, and increasing the internal quantum efficiency remains an issue.

[Problems to be Solved by the Invention] Conventional tunnel junction light-emitting devices have a drawback in that their light emission output is low and it is difficult to apply them to actual products. The reason why high luminous output cannot be obtained is that there are many defects in the luminescent layer.
This is because the injected carriers recombine non-radiatively. Therefore, it is required to grow a light-emitting layer with fewer defects, and to increase the injected carrier concentration so that the defect density does not affect the light-emitting efficiency as much as possible.

The purpose of the present invention is to solve the above-mentioned drawbacks of the prior art,
An object of the present invention is to provide a tunnel junction light emitting device that can increase the light emission output to a practical level.

[Means for Solving the Problems] The present invention provides a semiconductor thin film with a wide forbidden band width, an intrinsic semiconductor layer serving as a light emitting layer, a semiconductor thin film with a wide forbidden band width, and a semiconductor thin film with a wide forbidden band width on a semiconductor substrate having one conductivity type. It is applied to a tunnel junction light emitting device in which semiconductor layers having a conductivity type opposite to the conductivity type are sequentially laminated, and electrodes are formed on both sides of a semiconductor substrate in which these layers are laminated.

In such a tunnel junction device, a conduction type semiconductor layer and an opposite conduction type semiconductor layer include GaAS or Ga
The device uses AIAs, ZnSe is used for the two semiconductor thin films with wide forbidden band widths, and GaAlAs is used for the intrinsic semiconductor layer.

Then, intrinsic Ga becomes an injection layer for injected electrons and holes.
In order to facilitate radiative recombination at the center of the AlAs layer, it is preferable to configure the mixed crystal profile of the intrinsic GaAIAsFj so that the forbidden band width is narrowest near the center in the thickness direction.

The reason why ZnSe was selected from II-Vl group compound semiconductors as a compound semiconductor with a wide bandgap applicable to the present invention is because it has a lattice constant close to that of other semiconductors such as GaAs and GaAlAs.

[A semiconductor thin film with a wide forbidden band width, an intrinsic semiconductor serving as a light-emitting layer, a semiconductor thin film with a wide forbidden band width, and a semiconductor thin film with a conductive type opposite to the above one conductivity type are formed on a semiconductor substrate having a conductivity type of the above one. When semiconductors are sequentially laminated, they can all be formed by epitaxial growth, which facilitates manufacturing.

In addition, GaAs is used as one conductivity type semiconductor and the opposite conductivity type semiconductor.
Alternatively, using GaAlAs, Z
When nSe is used and GaAlAs is used as the intrinsic semiconductor,
Since these lattice constants are very close, a light-emitting layer with few defects is formed.

In addition, if the GaAlAs layer that becomes the light emitting layer has a mixed crystal ratio profile such that the forbidden band width is smallest near the center, the amount of injected electrons and holes will increase due to the formation of an internal electric field. This increases the injected carrier concentration. Also,
The injected electrons and holes are collected at the center of the light emitting layer. The electrons and holes collected at the center of the light-emitting layer have the smallest forbidden band width at the center and are spatially very close to each other, so that they are efficiently recombined radiatively.

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

The tunnel junction light emitting device of this embodiment uses a double tunnel junction to utilize the tunnel effect of holes as well as electrons, and uses a semiconductor with a wide forbidden band width instead of an insulator.

Its basic structure is to sequentially stack a semiconductor thin film with a wide bandgap, an i-type semiconductor, a semiconductor thin film with a wide bandgap, and an n-type semiconductor on a p-type semiconductor substrate. It forms the

GaAS or GaAIAs is used as the p-type semiconductor and n-type semiconductor, ZnSe is used as the semiconductor with a wide forbidden band width, and GaAs is used as the i-type semiconductor.
An lAs layer is used.

Next, the tunnel junction light emitting device structure of this example will be specifically explained using FIG. p-type G on p-type GaAs substrate 6
An aAs layer is grown to a thickness of 2 μm, and a ZnSe thin film 5 having a wide forbidden band width and high resistance is grown thereon by 50 people. Next, the i-type GaAIA SF! which becomes the light emitting layer. 4 was grown, but the mixed crystal ratio profile was A at the center of the thickness direction.
The IAs mixed crystal ratio is 0, and the AlAs mixed crystal ratio is 0 on both end faces.
It is assumed that the epitaxial layer is 1. This l-type Ga
A ZnSe thin film 3 with a wide forbidden band width was grown by 100 people on AIAsFj4, and 5 μm of n-type Ga AIA s Pi 2 with an AlAs mixed crystal ratio of 0.2 was grown thereon. An n-side electrode and a hp-side electrode 7 were formed on each of the front and back sides of the epitaxial wafer thus formed.

Here, the semiconductor material of the light emitting element is GaAs, GaA
lAs5ZnSe is used because the lattice constants of these semiconductors are very close to each other. Therefore, GaAlAsF! becomes a light emitting layer! 4 can be grown as an epitaxial layer with few lattice defects.

Moreover, as shown in FIG. 1, the electrons 9 are n-type GaAlAs
From layer 2, the l-type Ga passes through ZnSe3 with a wide forbidden band width.
Holes are injected into the AlAs layer 4 by the tunnel effect, and holes 1
0 passes through ZnSe5 having a wide forbidden band width from the p-side electrode 7 and is injected into the i-type GaAlAsN4 by a tunnel effect, and light 8 is emitted. In this case, GaAlA
Since sFj4 has a mixed crystal ratio profile such that the forbidden band width is smallest near its center, the electrons 9 injected through each ZnSe thin film 3 and 5 provided on both sides
The holes 10 and
sF'4) concentrated in the center.

It is thought that the electrons 9 and holes 10 collected at the center of the light-emitting layer are efficiently recombined radiatively because the forbidden band width is the smallest at the center and they are very close to each other spatially.

When we actually manufactured this element and applied a negative voltage to the n-side electrode l and a positive voltage to the p-side electrode 7, we found that as the voltage was increased, the peak wavelength shifted to the shorter wavelength side (higher energy side).
It has been confirmed that lowering the voltage V causes a shift to lower energy, and the emission wavelength has been controlled between 800 nm and 880 nm.

Furthermore, a light emission output of 0.1 mW was obtained, which was a value that could be used in practical use as a device.

As described above, according to this example, the metal constituting the conventional tunnel junction light emitting device is replaced with a semiconductor, and the insulator is replaced with a semiconductor with a wide forbidden band width. can be formed. Furthermore, since we selected semiconductors with lattice constants similar to these semiconductors, it is possible to form an epitaxial layer with fewer lattice defects.

In addition, we made the tunnel junction a double junction to utilize not only the tunnel effect of electrons but also the tunnel effect of holes.
The peak wavelength can be controlled by voltage, monochromatic light with a small tail on the long wavelength side can be obtained, and high luminous efficiency can be obtained.

Furthermore, by increasing the internal quantum efficiency by setting the mixed crystal ratio profile of the light-emitting layer to the smallest value at the center, it is possible to increase the injected carrier concentration and prevent the defect density from affecting the light-emitting efficiency as much as possible.

Therefore, it can contribute to applications in various fields such as the sensor field.

In the above embodiment, epitaxial growth was performed on a p-type substrate, but an n-type substrate may be used and an epitaxial layer of the opposite conductivity type to that of the p-type substrate may be grown thereon.

[Effect of the invention] According to the present invention, the following effects are achieved.

(1) According to the tunnel junction light emitting device according to claim 1, since the semiconductor layers stacked on the substrate are made of semiconductors having similar lattice constants, it is possible to grow a light emitting layer with few defects. It is possible to increase the luminous output to a practical level.

(2) According to the tunnel junction light emitting device according to claim 2, since the mixed crystal profile of the light emitting layer is such that the forbidden band width is narrowest near the center, the implantation concentration is increased to reduce the influence of defect density. You can avoid receiving it as much as possible,
The light output can be further increased.

[Brief explanation of the drawing]

FIG. 1 is a band structure diagram of a tunnel junction light emitting device according to an embodiment of the present invention, FIG. 2 is a sectional view of a tunnel junction light emitting device structure according to this embodiment, and FIG. 3 is a cross section of a conventional tunnel junction light emitting device structure. It is a diagram. 1... n-side electrode, 2... n-type GaAlAs layer, 3...
...ZnSeF! , 4-GaAlAs layer, 5-Z n
S e layer, 6... p-type Ga AS layer, 7...
p-side electrode, 8... emitted light, 9... electron, 10...
Hole.

Claims (1)

[Claims] 1. A semiconductor thin film with a wide forbidden band width, an intrinsic semiconductor layer serving as a light emitting layer, a semiconductor thin film with a wide forbidden band width, and a semiconductor thin film with a wide forbidden band width, on a semiconductor substrate having a conductivity type (1), which is opposite to the conductivity type (1) above. In a tunnel junction light emitting device in which semiconductor layers having conductivity types of 1 and 2 are sequentially stacked and electrodes are formed on both sides of a semiconductor substrate in which these layers are stacked, it is prohibited to use GaAs or GaAlAs in one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer. Zn in wide band semiconductor thin film
A tunnel junction light emitting device characterized in that Se is used for the intrinsic semiconductor layer and GaAlAs is used for the intrinsic semiconductor layer. 2. The tunnel according to claim 1, wherein the intrinsic semiconductor layer using GaAlAs has a mixed crystal ratio profile such that the forbidden band width is narrowest near the center in the thickness direction. Junction light emitting device.