Light-emitting device

Start of patent period: 1980 02 15 Longest possible duration:

B Issued on: 1980 09 25

Inventor:

© dependence:

© Pamphlets considered to delineate the prior art:

ELECTRONIC NO. 7/1976, S.EL 39

- 2 No. 358639

The invention relates to a light-emitting semiconductor device in which a layer of n-type gallium nitride is applied to a layer of sapphire.

The invention can be in display devices, in color television or as an optocoupler in control circuits that operate in continuous or pulsed mode or the like. be used.

There is known a planar-semiconductor light-emitting device in which an insulating polycrystalline layer of gallium nitride GaN is deposited on a p-type silicon substrate by a high-frequency sputtering method, and a transparent layer of indium oxide is in contact therewith.

At an electric field strength of E = 10 V / cm and a supply voltage U = 10. , , , 30V, the recombination of injected charge carriers takes place in the layer consisting of gallium nitride, which produces a pale blue radiation whose critical wavelength is 0.48 pm (see, for example, US Pat. No. 3,849,707).

A disadvantage of the known device is the high electric field strength, which is close to about 10⁷ V / cm resulting breakdown field strength and is due to the recombination mechanism of unlike charges in the gallium nitride whose sources are the substrate and the metal contact.

In addition, the known device on a weak lights, which is invisible in daylight at a sufficiently high supply voltage (10 .... 30 V), which narrows the field of application of this device. In the known device, it is necessary to provide a complicated transparent contact due to the absorption of the radiant energy in the silicon substrate. This again complicates the manufacturing process for devices based on the known device. From the magazine "Elektroniker", No. 7/1976, p. EL39, an electroluminescent diode in the colors blue and green has become known in which a sapphiresubstrate, a layer of n-type gallium nitride and on this a layer of p-type gallium nitride is applied. This known diode is made on the principle of homogeneous transition and therefore has all the structural defects that underlie this principle. Due to the fabrication of the conductivity of p-type gallium nitride, this diode requires a complicated technological manufacturing process.

The purpose of the invention is to provide a light-emitting semiconductor device which has a violet glow and has wide applications.

The semiconductor device is also intended to emit visible light in a brightly lit room, which occurs at a supply voltage of less than 8 V by changing the nature of the charge injection mechanism in the device.

According to the invention, this object is achieved in that on the layer of n-type gallium nitride, a semiconductive layer of p-type aluminum nitride is supported, which forms an injection heterojunction with the layer.

It is expedient that the semiconductor layer of semiconducting gallium nitride and / or the semiconductor layer of aluminum nitride are semi-insulating.

The proposed light-emitting semiconductor device is characterized by bright radiation in a wavelength range of 0.43 to 0.48 pm and by simple construction and manufacture, a one-sided injection, a limited recombination range, and a high injection efficiency.

The invention will be explained in more detail with reference to exemplary embodiments with reference to the drawing, on which a light-emitting semiconductor device according to the invention is shown.

The light-emitting semiconductor device according to the invention comprises a substrate -1- of sapphire, to which an epitaxial semiconductor layer -2- of monocrystalline n-type gallium nitride GaN is applied. On the layer -2- a semiconductor layer -3- of p-type aluminum nitride AIN is applied, which forms an injection hetero-transition -4- with the layer -2-. On layer -3-, a metallic electrode -5- of aluminum and on the layer --2-- an indium electrode -6- is applied.

The layer -2- is formed on the substrate by epitaxial growth from a gas phase of single crystal gallium nitride; the layer -3- is produced on the Galliumnitrid existing layer -2- in the plasma process.

The layer -2 or 3- can be formed semi-insulating, which makes it possible to expand manufacturing capabilities for the production of the device.

- 3 No.358639

When current is supplied to electrodes -5 and 6-, carrier injection into the gallium nitride occurs due to the presence of the injection heterojunction -4- between the gallium nitride layer -3- and the aluminum nitride-made layer -4- and through the Recombination of charge carriers in said layer -2-- is caused. The radiation is conducted out of the semiconductor device via the substrate -1- as well as from the aluminum nitride existing layer -3-, which serves as an optical window.

The inventive light-emitting semiconductor device is characterized by an effective injection of charge carriers with a small electric field strength of not more than 1.5.10⁴ V / cm, a high uniformity of radiation over the entire surface of the device at voltages of 2.5 to 8 V out.

For a complete explanation of the invention, the following embodiments of the light-emitting semiconductor device will be cited.

Example 1: The device contains the following components:

a) substrate of sapphire (a-Al₂O₃) with orientation [0001], which is processed by mechanical means up to the 14th accuracy class, after which it is treated in a hydrogen stream at a temperature of 1500 to 1700 ° C;

b) epitaxial semiconductor layer of single-crystal n-type gallium nitride with a charge carrier concentration of about 4.10¹⁹ cm, with orientation [0001], wherein the thickness of this layer is 18 pm;

c) 0.1 pm thick semiconductor layer of p-type aluminum nitride;

d) the first 0.3 mm diameter electrode, formed by vapor deposition of aluminum on the layer of aluminum nitride;

e) second electrode, formed by melting indium on the gallium nitride layer.

When a forward biased voltage of 5 to 8 V is applied to the electrodes, radiation is observed from the side of the sapphire substrate. The radiation energy in the maximum of the spectral band is about 2.82 eV (T = 300 K).

Example 2: The device contains the following components:

a) substrate made of sapphire (ö-A1₂O₃) with orientation [0001];

b) epitaxial 8 pm thick layer of n-type gallium nitride with a charge carrier concentration of about 4.10¹⁹ cm *, with orientation [0001];

c) 0.03 pm semiconductor layer of p-type aluminum nitride;

d) the first electrode with a diameter of 0.3 pm, which is formed by vapor deposition of aluminum on the layer consisting of aluminum nitride;

e) second electrode, formed by melting indium on the gallium nitride layer.

As soon as a forward voltage of 2.5 to 5 V is applied to the electrodes, radiation from the substrate is observed. The radiation energy in the maximum of the spectral band is about 2.76 eV (T = 300 K).

CLAIMS

A light-emitting semiconductor device in which a layer of 45 n-type gallium nitride is coated on a layer of sapphire, characterized in that the

Layer (2) of n-type gallium nitride, a semiconducting layer (3) of p-type aluminum nitride is applied, which with the layer (2) an injection heterojunction (4) is formed.

2. A light-emitting semiconductor device according to claim 1, characterized in that the semiconductor layer (2) made of gallium nitride is semi-insulating.

- 4 No. 358639

3. Light-emitting semiconductor device according to the