JPH02252283A - Bistable light emitting device - Google Patents

Abstract

PURPOSE:To enable the high performance design and the high integration to be realized by a method wherein a resonance tunnel diode in asymmetrical structure is formed in a light emitting part so as to perform the bistable operations. CONSTITUTION:A resonance tunnel diode in an asymmetrical structure is formed between an emitter layer 8 and a base layer 12 while a laser diode is formed between an n type layer 3 and a p type clad layer 5. When the space between an anode electrode 7 and a cathode electrode 6 is impressed with proper voltage assuming the laser diode structure as a load series-connected to the resonance tunnel diode, two stabilized points in the high current state with high light emission and the low current state with low light emission exist in the voltage current characteristics. Furthermore, when a base electrode 13 is impressed with a specific pulse voltage, the two states in different intensities of light are brought about. Through these procedures, the bistable operation is realized so that the title light emitting device capable of selecting the light emitting wavelength and facilitating the enhanced performance and the high integration may be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-performance light emitting device capable of bistable operation and high integration.

[Conventional technology]

One of the devices that is attracting attention as an optical logic element used in optical computers and optical signal processing is a semiconductor light emitting device having bistable operation, and devices with various operating principles have been proposed. For example, Kawamura, Wakita, Asahi,
Oni (y, niawamuraK, Wakita, H,
Electronics Letter by Asahi and K, Oe)
s, Vol. 23° p. 721.1987). This device forms multiple quantum wells in the active layer (laser emitting part), utilizes differential negative resistance produced by resonant tunneling, and achieves bistable operation in combination with external resistance.

FIG. 4 shows a schematic cross-sectional view of a bistable light emitting device with a conventional structure. In FIG. 4, 1 is a substrate, 2 is an electrode lead layer made of a highly concentrated n-type semiconductor, and 3 is an n-type semiconductor made of an n-type semiconductor.
type cladding layer, 4 is a multi-quantum well active layer in which a semiconductor with a large forbidden band width and a semiconductor with a small band gap are alternately laminated, 5 is an n-type cladding layer made of a p-type semiconductor, and 6 forms an ohmic contact with the electrode lead layer 2. cathode electrode, 7 is n
This is an anode electrode that forms an ohmic contact with the mold cladding layer 5. Examples of materials forming this structure include semi-insulating GaAs as the semiconductor base Fi1, Aj2o, *Gao, tAs as the electrode lead layer 2, Aj2o, *Gao, tAs as the n-type cladding layer 3, Ak591 layer 3 + Gao, 7AS, and multi-quantum well active Layer 4 is GaAs and Aj2o, :lGa,
, 7As stacked structure, Alo as the n-type cladding layer 5,
3Gao, 7AS, Au5e as the cathode electrode 6, and AuZn as the anode electrode 7.

The operation of this conventional bistable light emitting device will be described below. When a forward bias is applied between the cathode and the anode to the structure shown in FIG. It is injected into the well active layer 4, where recombination occurs and laser light is generated. At this time, since a quantum level is formed in the multi-quantum well active layer 4, when the energy of the injected carriers exceeds this quantum level, a sudden drop in current occurs, and the current/voltage characteristics are differentially negative. Sexual resistance appears. In a device having differential negative resistance, hysteresis can be provided near the region exhibiting this differential negative resistance by adding an external resistor. Therefore, by adding an external resistor to the conventional bistable light emitting device shown in FIG. 4, bistable operation can be achieved.

[Problems to be Solved by the Invention] However, although bistable operation is possible in the conventional semiconductor light emitting device as described above, it has the following drawbacks, and improvement thereof is desired.

In the conventional structure, the region that determines the characteristics of the differential negative resistance and the region that determines the emission wavelength and electricity-to-light conversion efficiency are common, making it difficult to design for high performance. Furthermore, since the basis of bistable operation is negative differential resistance and external resistance, in order to advance the integration of such devices, it is necessary to create an external resistance region occupying a large area on the same substrate. This becomes a major obstacle to increasing the degree of integration.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of conventional bistable semiconductor light emitting devices and to provide a semiconductor light emitting device that can be highly integrated.

[Means to solve the problem]

The bistable light emitting device of the present invention includes: an emitter layer made of an n-type first semiconductor; an emitter barrier layer made of a second semiconductor having higher conduction band energy than the first semiconductor and having a thickness that allows electron tunneling; A well layer consisting of a third semiconductor having a conduction band energy lower than that of the second semiconductor and having a thickness less than the electron wavelength, and a fourth semiconductor having a conduction band energy higher than that of the first semiconductor, which tunnels electrons from an emitter barrier layer. a base barrier layer having a thickness with low probability; a base layer consisting of an n-type fifth semiconductor; an n-type cladding layer consisting of an n-type sixth semiconductor; and a light-emitting active layer consisting of a seventh semiconductor. and an n-type cladding layer made of a p-type eighth semiconductor.

[Effect]

In the bistable semiconductor light emitting device of the present invention, the tri-bistable operation is due to the intrinsic bistable characteristics in the resonant tunnel diode structure stacked in the light emitting part.

Since this technology has been realized, the design of the light emitting part can be freely selected, and since no external resistor is required, high performance design and high integration are possible.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. .

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present invention.

Components in FIG. 1 having the same reference numbers as in FIG. 4 are equivalent to those in FIG. 4 and perform the same functions. 8 is the first n-type
9 is an emitter barrier layer made of a second semiconductor having a higher conduction band energy than the first semiconductor and has a thickness that allows electrons to tunnel; 10 is a third emitter barrier layer having a conduction band energy lower than that of the second semiconductor. 11 is a base barrier layer made of a fourth semiconductor having a higher conduction band energy than the first semiconductor and having a thickness that has a lower probability of electron tunneling than the emitter barrier layer 9. , 12 is a base layer made of an n-type fifth semiconductor, 13 is a base electrode forming an ohmic contact with the base layer 12, and 14 is an active layer made of a seventh semiconductor and emits light.

In this structure, an asymmetrically structured resonant tunnel diode is formed between an emitter layer 8 and a base layer 12, and a ground layer 3 made of an n-type sixth semiconductor and a p
A laser diode is formed between the cladding layer 5 and the cladding layer 5 made of an eighth type semiconductor.

FIG. 2 is a band diagram for explaining the operation of the embodiment of the present invention. In FIG. 2, the same reference numbers as in FIGS. 1 and 4 are equivalent to those in FIGS. 1 and 4 and perform the same functions. EC is the conduction band edge, Ev is the valence band edge, E is the Fermi level, and EQ is the resonance level.

When a positive voltage is applied to the base layer 12 with respect to the emitter layer 8 from the thermal equilibrium state shown in FIG. 2, the emitter barrier layer 9. Well layer 10 and base barrier W311
A current begins to flow through the resonance level Eq formed by .

When the bottom of the conduction band of the emitter N8 becomes higher than the resonance level Eq, electrons cannot pass through this region, and the current decreases. This becomes the negative differential resistance region of the current/voltage characteristics. Now, when increasing the voltage, the base barrier layer 11
Since the tunneling probability of the well layer 10 is smaller than that of the emitter barrier layer 9, many electrons are accumulated in the well layer 10.

Therefore, from the emitter barrier layer 9 to the base barrier layer 11
The shape of the conduction band edge in the region (barrier region) that reaches the region (barrier region) is upwardly convex, and the reduction in the resonance level Eq due to voltage application is smaller than the value expected when no electrons are accumulated. Therefore, as the voltage increases, the voltage at which differential negative resistance appears moves to a higher voltage side than the voltage expected when no electrons are accumulated. On the other hand, when the voltage is lowered, the voltage at which the differential negative resistance appears becomes approximately equal to the voltage expected when no electrons are accumulated. This is because the resonance level EQ starts from a state lower than the bottom of the conduction band of the emitter N8, so that almost no current flows and there are also few electrons accumulated in the barrier region. in this way,
The asymmetrically structured resonant tunnel diode constructed between the emitter layer 8 and the base layer 12 has intrinsic hysteresis.

If we consider the laser diode structure between the n-type cladding layer 3 and the p-type cladding N5 as a load connected in series to a resonant tunneling diode, and select an appropriate cathode-anode voltage, the result will be as shown in Figure 3. characteristics can be obtained. Note that FIG. 3 is a schematic current/voltage characteristic, showing the current/voltage characteristic of the asymmetric resonant tunnel diode structure and the load characteristic of the laser diode structure with respect to this. According to this, there is a high current state with a large current (strong light emission) and a low current state with a small current (strong light emission).
There are two stable points (the emission is weak). These states exist stably, but the voltage ■.

Even if the potential of the base layer 12 is kept constant, the state can be switched if the potential of the base layer 12 is brought out of the hysteresis even for a moment. Therefore, by applying a pulse voltage to the base electrode 13, two states with different emission intensities can be realized, and bistable operation can be achieved.

As described above, according to the structure of the present invention, the bistable operation is realized by the intrinsic bistability in the resonant tunneling diode structure with an asymmetric barrier, so the design of the laser diode part can be freely selected. . Therefore, it is easy to select the emission wavelength and improve the performance. Furthermore, since no external resistor is required, high integration is easy.

Next, a specific example of the manufacturing method and structure of the device created according to this embodiment will be described. As a crystal growth method, MBE (Molecular Beam Cp
itaxy) to a thickness of 0.5μ on the GaAs substrate 1.
n-G with a donor concentration of 6×10111CII+-3 at m
aAs electrode extraction layer 2, n-GaAs emitter layer 8 with a thickness of 0.2 μm and a donor concentration of 1×10110l8″, 30 μm thick 1A1o, zGao, rAS emitter barrier N9, 60 μm thick 1-GaAs well layer 10, thickness 5
0 people's i-A I 0.2G a O,? As-based barrier layer 11, thickness 0.2 ym, donor concentration I
O"cm-' n-GaAs base layer 12, thickness 0.1
n-A1. with a donor concentration of 5X10"c'm-' in μm.
．． 3 Gaa,, As cladding layer 3, 0.5 pm thick, donor concentration I
cm-' p A lo, zG a 007A
The S cladding layer 5 was grown sequentially. The base H12 and the electrode lead N2 were exposed by etching for electrode formation. The cathode electrode 6 and the base electrode 13 are A u
It was formed by depositing and alloying Ge/Au. Further, the anode electrode 7 was formed by depositing and alloying AuZn/AU. A clear laser intensity bistability was demonstrated at 77 in this device.

In the above embodiments, GaAs/A is used as the semiconductor material.
Although only the IGaAs system was shown, InGaA
s/AI! I nAs/InP system, AI S b /
It is clear that the present invention can be applied to gasb-based semiconductors and other various semiconductors. Further, although the materials shown above are combinations in which the lattice constants are almost the same, materials with different lattice constants and strains may also be used. Although only a laser diode structure is shown as the light emitting part, a light emitting diode structure may also be used. Furthermore, the layered structure is not limited to one in which a light emitting section is placed on a resonant tunnel diode, but may be the opposite structure.

〔Effect of the invention〕

The bistable semiconductor light emitting device of the present invention allows for higher performance and higher integration of the light emitting section.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view of an embodiment of the present invention, Fig. 2 is a band structure diagram of the embodiment of Fig. 1, Fig. 3 is its current/voltage characteristic diagram, and Fig. 4 is a conventional bistable FIG. 2 is a schematic cross-sectional view of a light emitting device. 1... Substrate 2... Electrode extraction layer 3... N-type cladding layer 4... Multi-quantum well active layer 5... P-type rad layer 6. 7 ・ 8 ・ 9 ・ 10 ・ 11 ・ 12 ・ 13 ・ 14 ・ c v t Q Cathode electrode Anode electrode Emitter layer Emitter barrier layer Well layer Base barrier layer Base layer Base electrode Active layer Conduction band edge Valence band edge Fulmi level Resonance level @ 1 diagram

Claims (1)

[Claims] (1) an emitter layer made of an n-type first semiconductor;
an emitter barrier layer made of a second semiconductor having a higher conduction band energy than the semiconductor and having a thickness that allows electron tunneling;
A well layer consisting of a third semiconductor having a conduction band energy lower than that of the second semiconductor and having a thickness less than the electron wavelength, and a fourth semiconductor having a conduction band energy higher than that of the first semiconductor, which tunnels electrons from an emitter barrier layer. a base barrier layer having a thickness with low probability; a base layer consisting of an n-type fifth semiconductor; an n-type cladding layer consisting of an n-type sixth semiconductor; and a light-emitting active layer consisting of a seventh semiconductor. A bistable light emitting device characterized by having a structure in which a p-type cladding layer made of a p-type eighth semiconductor is laminated.