JPS61118732A - Optical bistable semiconductor element - Google Patents

Abstract

PURPOSE:To obtain an optical bistable semiconductor element which operates even with a high-speed light signal by forming a light emitting element on the same substrate with an optical bistable semiconductor laser which has a current unapplied area and a current applied area in a resonator closely to the current unapplied area. CONSTITUTION:The DH substrate formed by laminating an n-InP buffer layer 11, an InGaAsP active layer 12, and a p-InP clad layer 13 on an n-InP substrate 10 is etched to form a wafer. Then, the 1st p-InP current block layer 14, the 2nd n-InP current block layer 15, a p-InP buried layer 16, and a p-InGaAsP cap layer 17 are formed successively and two grooves 22 and 23 for forming a mesa stripe 20 converting the active layer 12 are formed at a wide part 24 and a narrow part 25. The current blocks are not grown on the stripe 20 at the wide part 24 as shown in figure (b), but as shown at the in figure (c) at the narrow part 25. Then, Cd is diffused at part 29 of a flat part close to the narrow part 25 to form a current path penetrating the current block layers 14 and 15, the cap layer 17 of AuZn is formed thereafter, and electrodes 26, 27, 30, and 28 are stuck.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is applicable to optical switching equipment and optical information processing bags r! The present invention relates to an optically bistable semiconductor device that is used for logical operations and information storage in applications such as , and which performs bistable operation using an optically bistable semiconductor laser.

(Prior Art) Research into ultra-high-speed optical logic operations and storage devices for processing large amounts of information signals at high speed is continuing. Conventionally, the current device, which uses a current switch as a basic block, has been used as a device for performing logical operations and storing electrical signals.
mode logic is known, and in recent years GaAs
Research is progressing on ultra-high-speed logic operations and storage devices using FETs (high electron mobility transistors), Josephson junction elements, and the like. However, high-speed digital information processing of a large amount of two-dimensional data such as image signals using electrical signals has limitations in terms of calculation speed, power consumption, etc. In addition, in an optical transmission signal exchange, once light is converted into an electrical signal, there are problems such as band limitation, distortion, and loss of wavelength information. For this reason, it is desired to realize an optical logic operation and storage device that can digitally process and store optical signals as they are in the form of light, which is compatible with information processing in two-dimensional arrays at high speed and broadband. Examples of such optical logic operation and storage devices include optical bistable elements using semiconductor etalons as described in the magazine Optical Engineering, Vol. An optical bistable semiconductor laser, etc., as described in the conference proceedings 517-15, can be considered.

Among these, optical bistable semiconductor lasers, which have their own oscillation and amplification functions, have great potential and are expected to be used. At present, optical bistable semiconductor lasers are actually used in systems as optical memories of time-division optical switches, etc., as described in Proceedings of the 1981 National Conference of the Institute of Electronics and Communication Engineers, 517-13. However, conventional optical bistable semiconductor lasers have the problem that the trigger light level increases as the optical speed increases, and currently the upper limit of the practical optical speed of this semiconductor laser is several hundred Mb.
It is thought to be about /s. Therefore, there was a problem with the calculation and memory of the Koumei at high speeds of about Gb/s or higher. In order to solve these problems, the following optical bistable semiconductor laser device has been proposed as shown in another application filed on the same day by the applicant of the present application.

FIGS. 2(a) to 2(d) are diagrams for explaining an optical bistable semiconductor laser device shown in the other application, and FIG.
yJ(a) is a diagram showing an example of the laser device. This laser device is configured such that bias light from a semiconductor laser 3 driven by a power source 4 can be applied to a current non-injection region of an optical bistable semiconductor laser 1 via an optical fiber 2. The current non-injection region is formed by etching a portion without an electrode close to the active layer, and the end face of the optical fiber can be moved close to the etched groove portion from above.

FIGS. 2(b), 2(c), and 2(d) are diagrams for explaining the operation of the optical bistable semiconductor laser device shown in FIG. 2(a). In FIG. 2(b), bias light P1 exists and the incident light amount P I
Injected current i and output light amount P when a=0 @ @ I
FIG. As shown in this figure, the figure (a)
In the laser device shown in FIG. P0 decreases rapidly at 1=ic. As described above, the laser device shown in FIG. 2A exhibits a hysteresis characteristic and has two stable points A and B of the output light amount P and Pl at tl=ll. In this laser device, the hysteresis loop is shifted to the low injection current side by the presence of the bias light P, compared to the case where there is no optical bias.

FIG. 2(d) shows that the injection current i=i in FIG. 2(b)
b, and the amount of incident light P1m when bias light P1 exists
and the output light amount P0. ．． FIG. If the incident light tp+ is increased from 0 when the output light amount Pa m t =P is at the first stable point A, the output light tP, ,
, increases rapidly at PI-”?, and thereafter the amount of incident light P,
, =P, the output light amount P0. ．． moves to the second stable point B where the output light amount P**t=PI with almost no decrease. In this figure as well, the presence of the bias light P1 reduces the rising light amount P of hysteresis compared to the case where there is no optical bias and only a current bias is applied.

21m(d) is a table showing the operation of the bistable semiconductor laser device shown in FIG. 8(8) with respect to the injection current i and the amount of incident light P1°. When the injection current i is i, the incident light P1
When m is 0, the bistable semiconductor laser device is located at one of the two stable points A and B in FIG. hold. In FIG. 2(b), when the bistable semiconductor laser device maintains one stable point B (output light amount Pi), when the injection current i is stopped once and then returned to ib, the output light amount P0. ．． changes in the order of B4D-A, and thereafter maintains the other stable point A (outgoing light tP,).

That is, the bistable semiconductor laser device is reset. In addition, in FIG. 3(c), when the bistable semiconductor laser device maintains the stable point A (output light amount P,), the incident light amount is set to P once, and when it returns to 0 again, the output light amount is P,. , is A→E4B
After that, stable point B (output light amount P1) is maintained. That is, the bistable semiconductor laser device is set.

In this way, the optical bistable semiconductor laser device shown in FIG. 2(a) operates in the same way as a normal optical bistable semiconductor laser to which only a current bias is applied, but the optical bistable semiconductor laser device shown in FIG. The amount of incident light required can be reduced. Therefore, the response to high-speed Hikari 100 is significantly improved.

(Problems to be Solved by the Invention) However, in the optical bistable semiconductor laser device of the type shown in FIG. 2(a), the means for applying bias light is provided independently from the optical bistable semiconductor laser. This results in an increase in size, which poses a practical problem.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical bistable semiconductor device that operates even with high-speed optical signals and has a small size.

(Means for Solving the Problems) According to the present invention, an optical bistable semiconductor laser having a current non-injection region and a current injection region inside a resonator, and an optical bistable semiconductor laser provided on the same substrate as the optical bistable semiconductor laser. An optical bistable semiconductor device is obtained, which is characterized by comprising a light emitting device formed adjacent to a current non-injection region.

(Function) The semiconductor device of the present invention is formed by integrating a light emitting element for applying an optical bias to a non-current injection region of an optical bistable semiconductor laser on the same substrate as the optical bistable semiconductor laser. Therefore, this device has excellent response characteristics to high-speed optical signals because an optical bias is applied to the optical bistable semiconductor laser, and is extremely compact because the light source for the optical bias is integrated into one body. It's practical.

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

FIG. 1 is a perspective view showing an embodiment of the present invention.

The optical bistable semiconductor laser used in this example was invented by Mr.
As shown in Fig. 22, the outer side surface of the two grooves forming the mesa stripe (including the active layer) of a dual channel brainer buried heterostructure semiconductor laser (DC-PBH-LD) The opposing surfaces) partially protrude toward the mesa stripe side, and some of the grooves are narrowed. 3(a) is a planar sectional view showing the shape of the active layer of the optical bistable semiconductor laser used in the embodiment of FIG. 1, and FIG. 3(b) and (C) are A of FIG.
-A' and BB' arrow cross-sectional views. First, the optical bistable semiconductor laser used in this example will be explained with reference to 3S(a) to 3S(c).

This optical bistable semiconductor laser is based on a DC-PBH type in which a mesa stripe including an active layer is buried with p- and n-type semiconductor layers. Detailed information on 1984-166666, Figure 3 (
The structures shown in a) to (c) are manufactured as follows.

First, an n-InP buffer layer 11, a non-doped InGaAsP active layer 12, and a p-InP buffer layer 11 are grown by liquid phase or vapor phase growth.
A DH substrate formed by laminating an InP cladding layer 13 on an n-InP substrate 10 is coated with photoresist and subjected to ordinary photolithography and etching treatment to produce a wafer having the shape shown in FIG. 1. 6 Next, on this wafer, a first current blocking layer 14 of p-InP, a second current blocking layer 15 of n-InP, a p
-InP buried layer 16, p-InGaAsP layer
A layer 17 is sequentially formed. As shown in FIG. 3(a), the side surfaces of the two grooves 22 and 23 for forming the mesa stripe 20 including the active layer 12 are straight on the side of the mesa stripe 20; On the opposite side, it overhangs in the center. The grooves 22.23 therefore have a wide portion 24 and a narrow portion 25. In the second crystal growth, grooves 22. which form mesa stripes 20 are formed.
In the wide part 24 of the groove 23, as shown in FIG. 3(b), the first and second current blocking layers 14.15 do not grow on the mesa stripe 20; In the narrow portion 25, as shown in FIG.
．． Since the first current blocking layer 14 fills the inside of the mesa stripe 23, the shape near the mesa stripe 20 immediately before the second current blocking layer 15 is grown becomes flat.
The second current block 15 covers the entire top of the mesa stripe 20 without interruption, which is the groove 22° 23 of the fabricated optical bistable semiconductor laser wafer.
Cd is selectively diffused only above one part 29 of the flat part close to the narrow part 25 of p,
A current bus is formed by passing through the first and 29th current blocking layers 14 and 15 made of n-InP. AuZn is deposited on the cap layer 17 in order to establish a p-side ohmic contact with the wafer thus formed. A portion A of the groove 23 immediately above the narrow portion 25 of the groove 22 and 23 and near the area 29 where selective diffusion was applied by applying a Kira Camphor photoresist and performing normal photolithography and etching.
The uZn and cap layers 17 are sequentially removed, and a subsequent heat treatment is performed to alloy the interface between ΔuZn and the semiconductor layer, reducing the resistance between them.Next, the n-InP substrate 10 is polished to a thickness of about 120 mm. After this, Au-Ge-Ni is deposited for an ohmic contact on the n side, and heat treatment is performed to form an ohmic contact to complete the wafer production. This wafer is separated by a conventional arm-opening method to form a resonator surface perpendicular to the mesa stripe 20.

The first and second p of this element (II tolerance 26.27 positive,
As is already known, when the n-side electrode 28 is negatively biased, this device works as an optical bistable semiconductor laser having two levels that are stable with respect to current input or optical input.This is for the following reason. In other words, in the wide groove portion 24,
While current is injected into the active layer 12 as in the conventional buried heterostructure semiconductor laser, the narrow groove width portion 2
5, the second current blocking layer 15 is the mesa stripe 2
Since it is completely formed throughout including the upper part of 0,
No current is injected into the active layer 12, so *
21? ! [Since the lower part acts as a saturable absorption region, a saturable absorption region and a gain region are formed in the resonator, making it possible to realize optical bistable operation.

On the other hand, when the third p-side electrode 30 is positively biased, the current flows through the selectively diffused region 29 to the active layer 12 in the flat area.
I can inject Banko. In other words, this portion functions as a light emitting diode, and the output light from this light emitting diode portion passes through the InP layer with low light absorption that fills the trench 23 and irradiates the current non-injected region of the active layer in the mesa stripe. In other words, the light output from the light emitting diode serves as a light bias to the current non-injection region. Depending on the presence of this optical bias, the response speed of the optical bistable semiconductor laser to high-speed optical signals can be significantly improved. Moreover, in this embodiment, since the means for applying an optical bias (light emitting diode) is integrated with the optical bistable semiconductor laser, this embodiment is extremely compact and practical. In addition, the integrated light source for providing optical bias can also be used as a second optical input signal source, and in this case, logical operations etc. between it and the normal optical input signal source can be used. can be done. Furthermore, in this embodiment, if the fluctuations in the hysteresis characteristics of the optical bistable semiconductor laser due to temperature changes are known in advance, it is possible to compensate for the fluctuations in the hysteresis characteristics to some extent by changing the optical bias.

In this embodiment, a light emitting diode is provided as a light emitting element serving as a light source for optical bias, but the present invention can also be realized using a distributed feedback semiconductor laser or the like. Further, the optical bistable semiconductor laser may be any type as long as it has a current injection region and a current non-injection region, and the present invention is not limited to the structure of the embodiment.

Furthermore, although an InGaAsP/InP semiconductor material is used in the embodiment, it goes without saying that other materials such as GaAlAs/GaAs may also be used.

(Effects of the Invention) As described above in detail, according to the present invention, it is possible to obtain a compact and practical optical bistable semiconductor device that operates even with high-speed optical signals. Therefore, the present invention greatly contributes to the practical application of optical switching equipment and optical information processing equipment.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2(a) is a diagram showing the configuration of a separately proposed optical bistable semiconductor laser device, and FIG. 2(b) and (c) are views of the laser. A characteristic diagram of the device; FIG. 3(d) is a diagram showing the operation of the laser device in response to input; FIG.
b) and (c) are respectively book 130 (a) A-A
' and BB' arrow sectional views. DESCRIPTION OF SYMBOLS 1... Optical bistable semiconductor laser, 2... Optical fiber, 3... Semiconductor laser, 4... Power supply, 10... Substrate, 20... Mesa stripe, 21.22.23.2
4.25...Groove, 11.12.13,14°15,1
6.17...Semiconductor layer, 26.27.28.30...
- Electrode, 29... selective diffusion region. Fig. 1 2822jA 23 grooves (b)

Claims (1)

[Claims] An optical bistable semiconductor laser having a current non-injection region and a current injection region inside a resonator, and a light emitting element formed on the same substrate as the optical bistable semiconductor laser and close to the current non-injection region. An optical bistable semiconductor device characterized by: