JPS5967680A - Photo bi-stable element - Google Patents

Abstract

PURPOSE:To enable low current operation at a room temperature by a method wherein the opposite side of the mesa stripe of a groove for forming a mesa stripe is formed uneven. CONSTITUTION:The mesa stripe 20 sandwiched by two grooves 21 is formed on a double hetero substrate wherein an N type buffer layer 11, a non-doped active layer 12, and a P type clad layer 13 are formed on a substrate 10. The grooves 21 are so formed as to have an unevenness on the opposite side of the mesa stripe 20. Successively, a P type and an N type current block layer 14 and 15, a P type buried layer 16, and a P type cap layer 17 are formed by performing the second crystal growth. At this time, the current block layers 14 and 15 do not grow on wider mesa stripes 20a of the grooves 21. When electrodes 31 and 32 are provided on such an element, the electrode 31 is biased positively, and the electrode 32 negatively, the element operates as a photo bi-stable element having two levels stable for a current input or a photo input.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical bistable element using a semiconductor and which is a main component of an optical logic circuit.

Optical logic circuits are expected to be new logic circuits capable of operating at higher speeds than conventional electronic logic circuits, and fundamental studies have begun. One of the main components of optical logic circuits is an optical bistable element. Several configurations have been considered, but one using semiconductor materials is attracting attention as the one that can best utilize its high-speed performance. The current injection part of the double hetero (IJH) semiconductor laser is discontinuous in the direction of the cavity axis, forming a non-uniform current distribution in this direction. Some devices have achieved optical bistable operation due to the supersaturation absorption effect in areas where the first flow is small. Regarding this, please refer to the Electronics Letters (Electro-nic Letters)
Letters), Volume 17, 167K to 168
I am familiar with the papers reported to the devil. Optical bistable operation was achieved using a device with this structure, but the transverse mode is unstable because this device has a so-called planar structure that controls the transverse mode by limiting the width of current injection. Not only that, but the generation threshold is high and operation at room temperature is difficult.
It is hard to say that it is a practical element.

An object of the present invention is to provide an optical bistable element capable of low current operation using a chamber crystal.

According to this invention, the mesa stripe including the active layer formed by two substantially parallel grooves reaching the active layer is formed of a semiconductor layer including at least a semiconductor layer of a conductivity type different from the semiconductor layer above the mesa stripe. In the buried buried heterostructure semiconductor laser, the above! An optical bistable device characterized in that at least a part of the side surface of the substrate opposite to the mesa stripe is uneven, and the upper part of the mesa stripe is partially covered with the semiconductor layer of the different conductivity type. is obtained.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a plane +6? showing the shape of the active layer of the first embodiment of the present invention. Figure 2 is A-A/ of Figure 1.

Here are the cross-sectional views of the B-B/section. This embodiment has a planar buried heterostructure in which two grooves forming a mesa stripe including an active layer have a partially narrowed side surface on the opposite side from the mesa stripe. . A planar type buried heterostructure semiconductor laser is one in which a mesa stripe including an active layer is buried with p and n type semiconductor layers, and this is disclosed in the invention pending by Kitamura et al. I am familiar with This example is manufactured as follows.

First, by a normal liquid phase growth method, an n-10P back 7 layer Ill non-doped InU was formed on an n-1,P plate 10.
A photoresist is coated on an IJH substrate on which an aAsP active layer 12+p-1nP cladding layer 13 is formed, and a wafer having the shape shown in FIG. 1 is manufactured by ordinary photolithography and v-etching.

Subsequently, this wafer is placed in a growth furnace and a second crystal growth is performed. First, a first current blocking layer 14 of p-10H + a second current blocking layer 15 of n-1nP is formed, and then a buried layer 15 of p-1,H + p-1nGaAsP is formed.
A cap Ifl17 is formed. As shown in Figure 1, the two grooves 21 for forming the mesa stripe 20 including the active layer are @ lines on the side of the mesa stripe 20, and protrude and retract at intervals on the side away from the mesa stripe 20. Thus, it has a wide portion 20a and a narrow portion 20b.

In the second crystal growth, in the wide portion 20a of the groove 21 forming the mesa stripe 20, as shown in FIG. 2(a), the first. Second current blocking layer 14115
does not grow on mesa stripe 20. On the other hand, groove 2
In the narrow portion 20b of the first current blocking layer 14, the second current blocking layer 14 fills the inside of the groove 21.
Since the shape near the mesa stripe 20 immediately before the growth of the mesa stripe 5 becomes flat, the second current blocking layer 15 covers the entire mesa stripe 20 without being interrupted at the upper part thereof. Details of such crystal growth can be found in the above-mentioned Japanese Patent Application No. 166666/1983.

After the crystal growth is completed, an Au-Zn p-side electrode 31 is formed on the surface of the cap layer 17, and an Au-(je-Ni
The n-side electrode 32 is formed by steaming and alloyed.
- Finish the production of. A device is fabricated by forming a resonator surface perpendicular to the mesa stripe 20 by using a normal cleavage method on this wafer.
When the side electrode 32 is negatively biased, the device functions as a two-level brightness-gazing device that is stable to current or light input. This is due to the following reason. That is, in the wide groove width portion 20a, a current is injected into the active layer 12, similar to the conventional buried laser, whereas in the narrow groove width portion 20b, a second current of n-10)' is injected into the active layer 12. Blocking layer 1
5 is formed over the entire surface including the upper part of the mesa stripe 20, no current is injected into the active layer 12. Therefore, a non-uniform current is injected in the axial direction of the resonator, and a saturable absorption part and a gain part are formed during co-imaging, and an optical bistable element is realized. Unlike conventional optical bistable devices, this device has a so-called buried structure in which the active layer is embedded in a semiconductor layer.
It can be easily operated at room temperature with low operating current.

In this example, @tea threshold 1 shift is approximately 40 mA, and l
Low current operation of less than oOmA was possible.

As explained above, in this invention, based on consideration of the state of crystal growth in the groove on and around the mesa stripe, the groove shape of the planar buried semiconductor laser is changed so that the side surface opposite to the mesa stripe is By stacking semi-isomers of different conductivity types, I-stripes, on top of the methystrives in the central part of the s4 width, a non-uniform DC distribution can be realized, and light A bistable element is obtained.The dimensions of the element in this implementation row are as follows: mesa stripe 20
The width of the groove is 25μm + the width of the wide part 20a of the groove is 7μ + 1
1 + central part 20b width is 3 μm, wide line width part 20
The length of a is 40μm + the length of the end portion 20b is 10
It is μm. Since the appearance of crystal growth varies greatly depending on the growth method, growth conditions, etc., it goes without saying that appropriate dimensions should be adopted in conjunction with these factors. Further, in this embodiment, the length ratio of the wide groove portion 20a to the narrow groove portion 20b is set to 4:1, but it is not limited to this one length.

Figure 3! FIG. 4 is a plan view showing the groove shape of the twenty-first third embodiment of the present invention. Second fruit! In the example, the narrow groove width portion 20b is placed in the center of the element ii
It's L. L-kun 3's barun+ri+I? Well, it is constructed by having one wide groove portion 20a and one narrow groove portion 20b. In these examples as well, MeC bistable devices capable of low current operation at room temperature were obtained. In the above examples, the semiconductor material is L H)' / l
n (j B A SP Not limited to G3As/AI
Other materials such as UaAs are also suitable. Furthermore, the uneven grooves 1Ijl1 surface need not be discontinuous as shown in the figure, but may be smoothly changing.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the active layer of the first embodiment of the present invention, FIG. 2 is a sectional view thereof, and FIGS. A plan view of the surface including the active layer of the third embodiment is shown. In the figure, 10...substrate, 11...
Buffer 1, 12... γ 1st life) Zeng, 13.
...Clad layer, 1415...g (Flow prevention layer, 16...Buried layer, 20...
Mesa stripe, 21...groove, 20a...
...The wide groove width r, 1; minute, 20b...The same wide part is covered respectively.ヱ〕 ″, -40: Kyou! Concave 32

Claims (1)

[Claims] The active layer and the first and second layers sandwiching the active layer and having a larger energy gap, a smaller refractive index, and different conductivity types.
A mesa stripe formed of two substantially parallel grooves reaching the active layer is formed by at least a semiconductor layer including a third semiconductor layer having a conductivity type different from that of the semiconductor layer on the upper surface of the mesa stripe. In the buried heterostructure semiconductor laser, at least a part of the side surface of the trench opposite to the mesa stripe is uneven, and the upper part of the mesa stripe is partially covered with the third semiconductor layer. An optical bistable element characterized by being covered with