JPH0812908B2 - Light emitting thyristor element and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a light emitting thyristor element used for optical communication and optical information processing.

[Conventional technology]

The light emitting element is an important key device in optical communication and optical information processing, but it is expected to realize an optical functional light emitting element that can be controlled by light input. The characteristics required for such an optical functional light emitting device are that the optical output can be turned on and off by an optical input signal, that the smallest possible optical input and high output optical output can be obtained, and high speed driving is possible. What you can do. In response to such a demand, an attempt to realize an element capable of turning on / off the optical output depending on the presence / absence of the optical input is made by using a light emitting thyristor element having a basic structure of pnpn type or npnp type. Such devices are described, for example, in Journal Applied Physics, 1986.
Volume 59 596 (GWTaylor et al., J.Appl.Phys.59,596 (1
986)). This device has a thin layer called the charge sheet layer because it is depleted between two n layers, but the behavior of the current-voltage characteristics is pn.
It is the same as that of a pn type (or npnp type) thyristor element. Therefore, this element will be discussed here as a light emitting thyristor element. Also, Applied Physics Letters, 1988, 52, 700 pages (K.Kasahara et al., Appl.Phys.Let
t.52,679 (1988)), the pnpn-type light-emitting thyristor element has the function of turning on / off the optical output by an optical input signal, and the electrical output of the signal again at a certain time after the optical signal is input. The dynamic memory function that can be read out in the form of optical output has been verified. An integrated element in which these element units are arranged in a matrix on a semi-insulating substrate is also being realized.

FIG. 2 is a schematic cross-sectional view of such a conventional element unit. In FIG. 2, 10 is a cathode electrode, 11 is a semi-insulating substrate, 12 is an n-type semiconductor clad layer, 13 is a p-type semiconductor gate layer, 14 is an n-type semiconductor gate layer, 15 is a p-type semiconductor clad layer, 16 Is an anode electrode. When a large number of these element units are integrated, it is necessary to increase the detection sensitivity commensurate with the reduction of the light emitting area and reduce the power consumption of the entire element. That is, it is necessary to improve the detection sensitivity per unit and reduce the power consumption per unit. But,
The conventional element structure has a problem that these improvements are not easy.

[Problems to be Solved by the Invention]

An object of the present invention is to provide a light-emitting thyristor element that solves the above conventional problems, efficiently detects an input signal, and consumes less power while maintaining a required optical output.

[Means for solving the problem]

The light-emitting thyristor element of the present invention comprises a light-absorbing / light-emitting layer composed of two layers, an n-type semiconductor gate layer and a p-type semiconductor gate layer, and a p-type semiconductor clad layer having a band gap larger than that of the light absorbing / light-emitting layer and an n-type semiconductor clad layer. In the light-emitting thyristor element laminated on the semiconductor substrate in the order of either pnpn or npnp, sandwiched between the
At least a part of the light emitting layer has a mesa structure, and a semiconductor current blocking layer having a band gap larger than that of the light absorbing / light emitting layer is provided on both sides of the mesa.

In addition, another method of manufacturing a light-emitting thyristor according to the invention is a semiconductor substrate in which a first conductivity type semiconductor clad layer, a second conductivity type semiconductor gate layer, and a first conductivity type semiconductor gate layer are sequentially stacked to absorb light. The first conductivity type semiconductor gate layer, which is a light emitting layer, is processed into a mesa shape, and the light absorption /
A first step of forming a semiconductor current blocking layer having a band gap larger than that of the light emitting layer; and removing the semiconductor current blocking layer on the mesa of the first conductivity type semiconductor gate layer by reactive ion beam etching, It is characterized by having at least a second step of covering with a two-conductivity type semiconductor clad layer.

[Operation and principle of the invention]

The operation principle of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an element of the present invention. In the light emitting thyristor element, the carrier density in the n-type gate layer is low when the element is in the off state. At this time, when light is input, electron / hole carriers are generated in the n-type gate layer, and a large device current can be efficiently supplied by the same mechanism as the current gain generation in the npn hetero bipolar. At this time, if the volume of the n-type gate layer is reduced and the power of the input light is concentrated on the small portion, the input signal sensitivity is increased. For this reason, the present invention limits the volume in the n-type gate layer to the mesa portion 17, and the current flowing through the element is also n.
By providing the semiconductor current blocking layer 18 beside the mesa,
I tried to squeeze it to 17. Further, a structure was provided in which the p-type clad layer 15 was grown so as to cover the convex portion of the mesa portion so that the input light was condensed to the mesa portion 17. That is, the operation of the configuration of the present invention is that the input signal sensitivity is increased, the current value for reaching a constant optical output is decreased, and the element unit size can be sufficiently reduced compared to the conventional structure, so that the element capacitance can be reduced. It is possible to speed up.

 Hereinafter, examples of the present invention will be described in more detail.

〔Example〕

FIG. 1 is a schematic element sectional view showing an embodiment of the present invention. In this embodiment, as shown in FIG. 1, first, a semi-insulating GaAs substrate is used.
N-type AlGaAs clad layer 12, p-type GaAs gate layer 13 having a thickness of about 50 Å, and n having a thickness of about 1 micron.
-Type GaAs gate layer 14, p-type AlGaAs cladding layer 15, and electrodes
10 and 16 are provided in the same manner as the conventional one, but part of the n-type gate layer 14 is provided with a mesa structure 17 and n-type AlGaAs is provided on both sides thereof.
The point that the current blocking layer 18 is newly provided is different from the conventional one. By providing this structure, the current flowing in the element concentrates on the mesa 17 of the n-type gate layer 14 which is a light absorption / light emitting layer, so that a small amount of current is injected into the mesa 17 compared to the conventional case. A large light output can be obtained.
In addition, as shown in FIG. 1, a p-type clad layer covering the mesa 17
Since the shape of 15 can be grown in a convex shape, the incident light 19 can be concentrated on the mesa portion 17 of the n-type gate layer, which is a light absorption region, by the lens action of the convex p-type cladding layer, and the input light intensity is lower than the conventional one. The signal can now be detected.

Hereinafter, a method for manufacturing the device of this example will be described in order with reference to the drawings.

FIG. 3 is a schematic process drawing showing an embodiment of the manufacturing method of the present invention. First, as shown in FIG. 3A, an n-type AlGaAs cladding layer 12 and a p-type GaAs gate layer 1 are formed on a semi-insulating GaAs substrate 11.
3. After growing the n-type GaAs gate layer 14 having a thickness of 1 micron, the n-type GaAs gate layer 14 was processed to form a mesa portion 17 having a width of about 2 μm. Then, as shown in FIG. 3 (b), n-type Al
The GaAs current blocking layer 18 was grown to about 0.2 μm. The Al composition ratio is 0.4, which is the same as the composition ratio of the cladding layer. The growth method was the molecular beam epitaxy (MBE) method. After that, the current blocking layer 18 above the mesa portion 17 was removed by the following method. First, a photoresist layer 31 is applied on the current blocking layer as shown in FIG. 3 (b), and then a reactive ion beam 32, chlorine ions in this embodiment, is applied as shown in FIG. 3 (c). By performing reactive ion etching 8, the current blocking layer above the mesa portion was removed.

Finally, after removing the photoresist layer 31 remaining in FIG. 3 (c), a p-type AlGaAs cladding layer was grown to form a smooth convex semiconductor structure as shown in FIG. The contact layer with the electrode, the electrode pattern, and the like were formed according to a normal optical device forming process.

The light emitting thyristor element formed according to the above process,
The volume of the mesa that contributes to light absorption and light emission is the number in the case of conventional elements
It was reduced to 1/10. For this reason, the light signal sensitivity is improved by the amount of light condensed on this portion, and further, the light output and the memory holding power consumption can be significantly reduced as compared with the conventional one. In addition, a device with good high-speed driving characteristics was obtained due to the reduction of the parasitic capacitance of the device.

In the above example, the shape of the structure covering the light absorption / emission mesa portion was formed in the shape of a cylindrical lens, but if the shape is a convex lens, higher sensitivity and lower power consumption are possible. is there.

In the above embodiments, the LED type light emitting element having a thick light absorption / emission layer is shown, but the same can be applied to a laser type light emitting element having a well in the layer. In addition, although the MBE method was used in the above-mentioned examples, metal organic chemical vapor deposition (MOCV
Other methods such as method D) may be used. Also, GaAs /
The present invention is basically effective not only for AlGaAls-based long-wavelength laser devices, but also for InP-based long-wavelength laser devices.

〔The invention's effect〕

As described above, the light emitting thyristor element of the present invention has characteristics of higher detection sensitivity for an input signal and lower power consumption of the element than conventional elements, and is suitable for application to an optical information processing element.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an embodiment of the present invention, FIG. 2 is a schematic sectional view of a conventional light emitting thyristor element, and FIG. 3 is a schematic process diagram of a method for manufacturing a light emitting thyristor of the present invention. 10 ... Cathode electrode, 11 ... Substrate, n ... N-type semiconductor cladding layer, 13 ... P-type semiconductor gate layer, 14 ... N-type semiconductor gate layer, 15 ... P-type cladding layer, 16 ... Anode Electrodes, 17 ... Optical absorption and emission mesa, 18 ... Current blocking layer, 19 ...
… Incident light, 31 …… Resist layer, 32 …… Reactive ion beam.

Claims (2)

[Claims] 1. A p-type semiconductor clad layer and an n-type semiconductor clad having a light absorption / emission layer composed of two layers, an n-type semiconductor gate layer and a p-type semiconductor gate layer, having a band gap larger than that of the light absorption / emission layer. In a light-emitting thyristor element which is sandwiched between layers and has a conductor type of pnpn or npnp stacked on a semiconductor substrate in that order, at least a part of the light-absorbing / light-emitting layer has a mesa structure, and A light emitting thyristor element characterized in that a semiconductor current blocking layer having a band gap larger than that of the light absorbing / light emitting layer is provided aside. 2. A first conductivity type semiconductor cladding layer, a second conductivity type semiconductor gate layer, and a first conductivity type semiconductor gate layer are sequentially stacked on a semiconductor substrate to form a light absorption / light emission layer. A first step of processing the semiconductor gate layer into a mesa shape, and forming a semiconductor current blocking layer having a band gap larger than that of the light absorption / light emission layer on the semiconductor gate layer; and a mesa portion of the first conductivity type semiconductor gate layer A method for manufacturing a light-emitting thyristor element, comprising at least a second step of covering the upper part of the semiconductor current blocking layer by reactive ion beam etching and then covering with a second conductivity type semiconductor clad layer.