JPH084149B2 - Optical element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical device having a non-injection region such as an edge-emitting diode and an optical bistable device.

[Conventional technology]

FIG. 3 is a cross-sectional view showing a conventional optical bistable device shown in, for example, Proceedings P140 of the 32nd Joint Lecture on Applied Physics.

In this figure, 1 is a semiconductor substrate of the first conductivity type, 2 is an active layer, 3 is a clad layer of the second conductivity type, 4 is a first electrode,
Reference numeral 5 is a second electrode, 6 is a back surface electrode, 7 is a first implantation region, 8 is a second implantation region, and 9 is a non-implantation region.

 Next, the operation will be described.

The current I _{1 is made} to flow between the back electrode 6 and the first electrode 4 in the state of being forward biased, and the current I ₂ is injected from the second electrode 5 in this state. The relationship between the light output and the current I ₂ at this time has different hysteresis when the current I ₂ increases and when it decreases, as shown in FIG. That is, this has the function of optical bistable.

Here, the non-injection region 9 is a so-called saturable absorber in which the absorption coefficient is large when the light output inside the element is small and becomes smaller as the light output increases. Is used to realize the above hysteresis characteristic.

[Problems to be solved by the invention]

In the conventional optical device as described above, the non-injection region 9 is first
The electrode 4 and the second electrode 5 are provided in a region where they are not formed so as not to flow an electric current.
Since the current spreads laterally from the electrode 4 and the second electrode 5, the area of the non-injection region 9 changes depending on the magnitude of the injection current, and it is difficult to obtain sufficient hysteresis characteristics. Otherwise, the entire non-injection region 9 will be injected depending on the injection current, resulting in a problem that the element size is limited.

The present invention has been made to solve the above problems, and an object thereof is to obtain an optical element that can obtain stable hysteresis characteristics even if the non-injection region is small.

[Means for solving problems]

An optical element according to the present invention includes a first conductivity type semiconductor substrate, a back electrode formed on the back surface of the semiconductor substrate, an active layer formed on the front surface of the semiconductor substrate, and an active layer formed on the active layer. A second conductivity type clad layer, first and second electrodes formed in regions on the clad layer that should be first and second implantation regions separated from each other, and the first and second The clad layer corresponding to the non-implanted region, which is the region between the implanted regions, the active layer, and the first or second conductivity type isolation region provided in a part of the semiconductor substrate. It was prepared.

Further, the isolation region is formed by diffusion of impurities.

[Action]

In the present invention, due to the difference in diffusion potential, current hardly flows into the isolation region in the non-injection region, and even if current flows into the active layer in the isolation region, only one type of carrier is injected, so the active layer is excited. Without becoming a stable saturable absorber.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of the optical element of the present invention.

In this figure, the same reference numerals as those in FIG. 3 indicate the same parts, and reference numeral 10 denotes a first or second conductivity type separation region.

 Next, the operation will be described.

When the current I ₂ is passed between the second electrode 5 and the back electrode 6 while the current I ₁ is passed between the first electrode 4 and the back electrode 6, hysteresis is generated as shown in FIG. Then, optical bistability is obtained, but at this time, the active layer 2 in the non-injection region 9 is
The isolation region 10 around the is of the first conductivity type or the second conductivity type, and the pn junction is a boundary portion with the isolation region 10 in the cladding layer 3 of the second conductivity type (the isolation region 10 is the first conductivity type). in the case of)
Alternatively, it can be formed at the boundary with the isolation region 10 in the semiconductor substrate 1 of the first conductivity type (when the isolation region 10 is the second conductivity type). In general, the diffusion potential of such a pn junction is higher than the diffusion potential formed in the active layer 2 of the first and second injection regions 7 and 8, so that the current flowing through the pn junction formed at the boundary of the isolation region 10 is increased. Is much smaller than the current flowing through the first and second implant regions 7,8. Further, even if this current flows into the active layer 2 in the non-injection region 9, only one type of carrier is injected, so this region is not excited by the current. As a result, the non-implanted region 9 can be a saturable absorber regardless of the current flowing through the first and second implanted regions 7,8. Therefore, sufficient hysteresis characteristics can be obtained regardless of the injection current, and the non-injection region 9 can be made small to reduce the element size.

The isolation region 10 can be formed in a step different from that of the first and second implantation regions 7 and 8 during crystal growth.
It is easy to form by diffusion of impurities.

In the above embodiment, the optical bistable element as the optical element having the non-injection region 9 is shown. However, as shown in FIG. 2, for example, the present invention is applied to the edge emitting diode having the non-injection region 9. In this case, a light emitting diode which does not oscillate even at a low temperature can be stably obtained. In FIG. 2, 11 is an electrode and 12 is an implantation region.

〔The invention's effect〕

As described above, according to the optical element of the present invention, the first
A conductive semiconductor substrate, a back electrode formed on the back surface of the semiconductor substrate, an active layer formed on the front surface of the semiconductor substrate, and a second conductive clad layer formed on the active layer, A region between the first and second implantation regions and the first and second electrodes formed in regions which should be the first and second implantation regions separated from each other on the cladding layer. Since the clad layer corresponding to the injection region, the active layer, and the first or second conductivity type isolation region provided in a part of the semiconductor substrate are provided,
The active layer in the isolation region becomes a stable saturable absorber, sufficient hysteresis characteristics can be obtained regardless of the injection current, and the non-injection region can be reduced to reduce the device size. There is.

Moreover, since the isolation region is formed by diffusion of impurities, there is an effect that the isolation region can be easily formed.

[Brief description of drawings]

1 is a sectional view showing an embodiment of an optical element of the present invention, FIG. 2 is a sectional view showing another embodiment of the present invention, and FIG. 3 is a sectional view showing an optical element having a conventional non-injection region. FIG. 4 and FIG. 4 are diagrams showing operating characteristics of an optical element having a non-injection region. In the figure, 1 is a first conductivity type semiconductor substrate, 2 is an active layer, 3 is a second conductivity type clad layer, 4 is a first electrode, 5 is a second electrode, 6 is a back electrode, and 7 is a first implantation. Area, 8 is second
Implantation region, 9 non-implantation region, 10 isolation region, 11 electrode,
12 is an implantation region. The same reference numerals in each drawing indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A semiconductor substrate of a first conductivity type, a back electrode formed on the back surface of the semiconductor substrate, an active layer formed on the surface of the semiconductor substrate, and a second electrode formed on the active layer. A conductive type clad layer, first and second electrodes formed in regions on the clad layer, which should be separated from each other to be first and second implantation regions, and the first and second implantation regions The clad layer corresponding to the non-implanted region which is the region between the two, the active layer, and the first or second conductivity type isolation region provided in a part of the semiconductor substrate. An optical element characterized by. 2. The isolation region is formed by diffusion of impurities.
The optical element according to the item.