JPH0632326B2 - Light emitting element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a light emitting device used for optical information communication using an optical fiber.

(Structure of Conventional Example and Problems Thereof) In recent years, optical communication using a combination of a light emitting element and an optical fiber is playing a central role in advanced information technology. The optimum light wavelength for an optical fiber for long-distance communication is 1.3 to 1.6 μm, and the optical transfer characteristics of other optical fibers are significantly deteriorated. Therefore, fiber communication using light of an arbitrary wavelength is impossible, which is an obstacle to direct image communication.

(Object of the Invention) In view of the above-mentioned drawbacks, the present invention provides a light emitting device capable of efficiently converting arbitrary light into light having a wavelength of 1.3 to 1.6 μm.

(Structure of the Invention) In order to achieve this object, the light-emitting device of the present invention comprises p-InP
It is composed of three layers in which p-In _0.53 Ga _0.47 As and a low impurity concentration p-InP are further formed on the substrate. With this configuration, the electrons in the carriers generated in InP by the short-wavelength light emitted from the InP side of the uppermost layer are In
_0.53 Ga _0.47 As is collected in the layer, where In _0.53
It is possible to emit light having a wavelength of 1.6 μm, which is unique to Ga _0.47 As.

(Description of Embodiments) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the structure of a light emitting device in one embodiment of the present invention. In FIG. 1, 1 is p-InP,
2 is p-In _0.53 Ga _0.47 As, 3 is p-InP, 4 is an Al film, 5 is irradiation light, and 6 is emitted light. The thickness of each layer 1, 2, 3 is 1
μm, acceptor concentration is 10 ¹⁷ cm ^-3 , 5 × 10 5, respectively
^{They are 17} cm ^-3 and 10 ¹⁸ cm ^-3 . The operation of the light emitting device having the above structure will be described below. FIG. 2 (a) is a sectional view of the semiconductor portion of this embodiment, and FIG. 2 (b) is an energy diagram. In Fig. 2 (a), 1 is p-InP and 2 is p-In _0.53.
Ga _0.47 As, 3 indicates p-InP, and in FIG. 2 (b), 5 is irradiation light, 6 is emission light, 7 is conduction band edge energy, 8 is Fermi level, and 9 is valence band edge energy. , 10 are electron wells, and 11 are hole wells. The Al film is for reflecting the emitted light 6 reaching the film surface and extracting it to the surface. InP
The bandgap of is larger than the bandgap of In _0.53 Ga _0.47 As,
The acceptor level of InP is at a higher energy position than the In _0.53 Ga _0.47 As acceptor level. For that purpose, p-InP
When p-In _0.53 Ga _0.47 As comes into contact with the p-In _0.53 Ga _0.47 As, holes near the surface of InP flow into the vicinity of the surface of In _0.53 Ga _0.47 As and reach thermal equilibrium. As a result, the energy diagram shown in FIG. 2 (b) is obtained. That is, a barrier and a depletion layer similar to the Schottky contact are formed on the surface of InP. Now on layer 1 I
When irradiating light with energy above the forbidden band of nP, InP
In the electron-hole pairs generated in the electron, electrons are collected in the electron well 10 by the electric field of the depletion layer. The electron is a well 11
It recombines with the holes inside and emits light with an energy band _{gap of} In _0.53 Ga _0.47 As. The wavelength of this light is 1.6 μm, and thus the irradiation light of short wavelength is converted into desired long wavelength light.

In the light emitting device of the present invention, the acceptor concentration of the layer 1 is sufficiently low, and the thickness of the layer is appropriately thin so that the depletion layer spreads throughout. As a result, the electron-hole pairs generated in layer 1 are collected on the surface and accumulated in layer 2 by the electric field without non-radiative recombination. The technique for forming each layer is sufficiently advanced as an epitaxial growth technique for manufacturing a laser diode. Therefore, there are few defects at the interface of each layer, and there is little loss in electron defects.

On the other hand, non-radiative Auger recombination in Layer 2 results in a hole concentration of 10 ¹⁸
Less important than cm ^-3 . Thus, the electrons accumulated in the well are efficiently radiatively recombined with the holes.

If the irradiated light contains light with an energy value intermediate between the forbidden band width of In _0.53 Ga _0.47 As and the forbidden band width of InP, it is absorbed by the layer 2 and the electron-hole pair is absorbed. Generate and 1.
It emits 6 μm light.

Although wavelength conversion can be performed using only In _0.53 Ga _0.47 As, absorption of short wavelength light is concentrated in a thin layer near the free surface, resulting in non-emission of generated electron-hole pairs. The loss is large. As in the present invention, InP is formed outside In _0.53 Ga _0.47 As.
To create a high electric field in the whole layer,
It eliminates the disadvantage of free surface and enables highly efficient wavelength conversion.

The semiconductor used may be p-type or n-type, and
The material of each layer is not limited to InP and In _0.53 Ga _0.47 As, but other suitable materials can be combined, and there is a wide range of degrees of freedom.

As described above, according to the present invention, a semiconductor having a forbidden band width of 0.7 to 1.0 ev corresponding to a wavelength band of 1.3 to 1.6 μm is sandwiched between two layers of semiconductors having a wider forbidden band width. Light of short wavelength
It can be efficiently converted into light with a wavelength of 1.3 to 1.6 μm and has great practicality in the optical communication field based on optical fibers.

[Brief description of drawings]

FIG. 1 shows the structure of the light emitting device of the present invention, FIG. 2 (a) is a sectional view thereof, and FIG. 2 (b) is an energy diagram. 1 …… p-InP, 2 …… p-In _0.53 Ga _0.47 As, 3 …… p-InP,
4 ... Al film, 5 ... Irradiation light, 6 ... Emission light, 7 ... Conduction band edge energy, 8 ... Fermi level, 9 ... Valence band edge energy.

Claims (1)

[Claims] 1. A semiconductor of one conductivity type having a forbidden band width of 0.7 to 1.0 eV is sandwiched by two layers of a semiconductor of the same conductivity type as the semiconductor having a forbidden band width wider than the forbidden band width.
A light emitting device having a layered structure, which emits light having a wavelength of 1.3 to 1.6 μm by irradiating light having a wavelength of 1.6 μm or less.