JPS5856489A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To deflect an optical beam along a stripe by forming an FET as a drive circuit for generating a light deflection for a semiconductor laser, controlling the gate voltage of an FET, thereby asymmetrically varying the carrier distribution in an active layer. CONSTITUTION:In the state that a voltage is applied between a p type side electrode 15 and an n type side electrode 16 in an ordinary laser oscillation, a carrier distribution in the active layer 8 is symmetrical. When 1-3V of a voltage is applied between the source 12 and the drain 14 of an FET by flowing a current through the drain electrode 14 of the FET and a voltage of -0.5-0.5V is applied between the gage 13 and the drain 14, a current flows into the region 17, becoming swept asymmetrical distribution is produced toward the current injecting direction, i.e., the carrier at the right end of the strip width in the layer 8 is increased. Accordingly, the optical beam can be deflected toward the right side. Since the current amount injected from the FET is controlled by varying the gate voltage of the FET, the light can be deflected at the desired angle.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductor light emitting device, and particularly to a composite device having a light deflection function.In recent years, semiconductor lasers and other active elements have been combined,
Alternatively, attempts have been made to construct a composite device by providing a semiconductor laser with a new function other than the light emitting device. This special number is a composite device that combines a light emitting device such as a semiconductor laser and a drive circuit, such as a transistor or FET.
Although it is possible to modulate light intensity, it does not have a light deflection function.

In semiconductor light-emitting devices that can perform not only optical intensity modulation but also polarization, photodetectors are arranged in spatially different locations to detect optical signals.
゛ If T is set so that a beam of light is incident, an optical multi-stage switch or an optical modulator can be constructed.

An object of the present invention is to provide a composite device in which a drive circuit for causing optical deflection is formed on the same substrate on which a semiconductor laser is formed.

The present invention is directed to a double heterostructure semiconductor layer having an active layer that causes laser oscillation, and first and second cladding layers that have a larger forbidden band width than the active layer and sandwich the active layer. A semi-insulating layer and a FET operation layer are sequentially arranged on the
A drain and a source are provided in the ET operating layer to form an FET, and a stripe-shaped impurity region defining a first current path through which current flows through the laser emitting region and a second current path adjacent to the first impurity region are formed. This is a semiconductor light emitting device having a light deflection function in which a stripe-shaped impurity region defining a path is provided and the second impurity region is connected to the source or drain of an FET.

In a typical semiconductor laser, a built-in waveguide or current injection region is formed in a stripe shape, and the operation is such that a radiation beam exists in a fixed direction along this stripe region and has a constant light intensity. This is to obtain the distribution.

In the present invention, an FBT is used as a drive circuit for causing optical deflection.
is provided to control the gate voltage of the FET, that is, the FE
By expanding the depletion layer in the T active layer, the carrier distribution in the active layer is changed and the light beam along the stripe f is deflected.

In order to realize such deflection, a phenomenon is utilized in which if an asymmetric carrier distribution is created in the vicinity of the stripe width of the active layer, the direction of the emitted beam deviates from the direction along the stripe. Physically, this is explained by the connection between the asymmetric light intensity distribution caused by the asymmetric carrier distribution and the spatial Fourier transform of the radiation beam.

The operating principle of optical deflection is briefly explained as follows.

In a typical striped semiconductor laser, some technique such as impurity diffusion, proton irradiation, I)n junction, etc. is used to narrow down the injection current within the stripe region and cause laser oscillation within this stripe width. ing.

Figure 1 is a schematic explanatory diagram to explain the situation.
The first semiconductor layer 1, which is an active layer that causes laser oscillation, is
A double heterojunction is formed between the second and third semiconductor layers 2 and 3, which have wider forbidden band widths. Oka, 4
is a stripe electrode, 5 is an electrode, S! each indicates a stripe area.

With this structure, carriers injected into the semiconductor layer 1 are effectively confined in the thickness direction, and as a result, the distribution of carrier concentration in the lateral direction (stripe width direction) is as shown in Figure 2. become. That is, carriers are distributed symmetrically from the center of the stripe.

In the above state, since the semiconductor layer 1 does not have a refractive index distribution in the lateral direction, a symmetrical near-field image, a neck, and a light emitting surface f as shown in FIG. A symmetrical far-field pattern, that is, a distribution in the radiation direction of light, is also obtained.

By the way, if it is possible to provide a difference in refractive index in the lateral direction in the semi-conductive layer l# by some method and make it asymmetrical, light can be deflected.

For example, if the refractive index is changed near the edge of the stripe as shown in Figures 4 and 5, the near-field and far-field images can be made to have asymmetry as shown in the figure. In particular, the far-field image can be deflected.

In the present invention, rather than combining a semiconductor laser and an FET on the same substrate, an asymmetric carrier distribution is created near the stripe width of the active layer, thereby realizing an asymmetric refractive index distribution. Note that θ shown in FIGS. 4 and 5 represents the deflection angle, and the island refractive index difference Δn depends on the stripe width and the like.

Hereinafter, the present invention will be explained in detail using examples. FIG. 6 is a perspective view of the semiconductor light emitting device of this example.

In the figure, 6 is an n-type gallium arsenide (GaAs) substrate, and 7 is an n-type gallium aluminum Φ arsenide (Ga0.7AtO, 3As) substrate with a thickness of 5 to 10 μm.
, 8 is GaO,97Ato with a thickness of 0.1 to 0.3 μm
, 03As active layer, 9 is p-type GaO with a thickness of 1 to 2 μm
, 7Ato, 3As cladding layer, 10 has a thickness of 0.5 to 1
μm n''' type GaAs semi-insulating layer 11 has a thickness of 0.2~
An active layer of an n-type GaAs FET with a 1 μm impurity concentration of 10 cm to 10 cm, 12 the source electrode of the FET, 13 the gate electrode of the FgT, 14 the drain electrode of the FET, 15 the p-side electrode, 16 is n91tlt pole, 1
Reference numeral 7 indicates a p-type stripe generation region formed by diffusing, for example, cadmium (Cd) or zinc (Zn). In this example, a non-1 for p-type stripe generation is used.
A second p-type stripe generation region 17' is formed adjacent to 7, and serves as an electrode for passing a current for laser oscillation to a main electrode, that is, a p@ electrode 15, and a current for changing carrier distribution. A control electrode, that is, a pole 14 is formed at the drain of the FET, and a current is caused to flow through the control electrode 14 to deflect light. Note that the p-type stripe generation region 17
and 17' are separated by etching,
This is to greatly change the carrier distribution of the stripe width of the active layer 8 and to effectively deflect light.

In FIG. 7, which is a cross-sectional view of the device shown in FIG. 6, S is the stripe width of the region 17, S is the stripe width of the region 17', and t1 is the distance between the regions 17 and Q17' and the active layer 8. If the distance between region 17 and region 17' is k, then Sl -3 to 20 [μm] S, -1 to 10 [μm] t -0,2 to 0.5 [μm] k -0,2 ~2 [4 m] is an appropriate range. The distance between regions 17 and 17' is shorter than the diffusion length of the injected carriers in the active layer)
However, if the stripe width S is too large, the control current will increase, which is not preferable.

As can be seen from FIG. 6, in the conductor light emitting device of this embodiment, the drive circuit that causes light deflection is located on the right side of the drawing.
That is, an FET is formed.

Next, the operation in this embodiment will be observed. Now, when normal laser oscillation is performed by applying a voltage between the p-side electrode 15 and the n11g electrode 16 without operating the FBT, the light beam is directed in the same direction as the stripe, that is, when the laser oscillates in the same direction as the stripe. It is radiated in a direction perpendicular to the open plane. The carrier distribution within the active layer 8 in this state is as shown by the solid line in the eighth factor. That is, depending on the current injected from the p-side electrode 15,
This produces a symmetrical distribution of carriers near the stripe width S. However, when the voltage between the source 12 and drain 14 of FgT is applied to 1 to 3V, and the voltage between the gate 13 and drain 14 is applied to -0.5 to 0.5V, a current flows into the region 17, and the broken line in FIG. As shown in Fig. 9, the distribution is such that the tail is drawn in the direction in which the current is injected. This is shown in Fig. 9 as a refractive index distribution.

That is, when no current is injected, the distribution is as shown by the solid line. Generally, when the carrier concentration is zero, it is flat as shown by the dashed line, but if the carrier concentration is as high as described above, it decreases by about 10-" to 10-3, and the refraction at that time The ratio n0 is approximately 3.52. Even if the refractive index becomes negative in this way, light is emitted as usual because of the carrier gain. However, when carriers are injected by operating the FET, the refractive index distribution changes drastically as shown by the broken line. That is, the leakage mode also becomes asymmetric.

Therefore, in a state where carriers are injected from the FET,
The wavefront of the light propagating on the right side of the stripe is advanced, and the traveling direction of the light is bent. This situation is shown in FIG. 10 as a schematic plan view.

As a result, as shown in FIG. 11, the light intensity distribution changes from a solid line without carrier injection to a broken line with carrier injection, resulting in an asymmetric distribution with respect to the directional shift.

The angle θ at which the light is deflected can be about 3° to 10′ and depends on the amount of current injection, that is, the FET gate voltage.

According to this practical example, by operating PET, the number of carriers at the right end of the stripe width in the active layer increases;
The carrier distribution becomes asymmetric and the light beam can be deflected to the right. Furthermore, the amount of current injected from the FET can be used to deflect the gate light of the FET to a desired angle.

I will introduce two modified examples of the Meio side.

The same parts as those observed in Figure 6 are indicated by the same symbols.

FIG. 12 shows the semiconductor laser device glue 2 rad layer 7 of FIG. 6.
FIG. 2 is a perspective view of a semiconductor laser device characterized by providing a step. When a clouding current is injected into the stepped portion of the cladding layer 7, a difference in refractive index is effectively created in the active layer 8 due to a change in the propagation constant of light guided in the thickness direction. The operations shown in FIG. 5 and FIG. 5 can be realized.

FIG. 13 is a sectional view of the semiconductor laser device of FIG. 12. If the thickness of the thinned portion of the cladding layer 7 is m, it can be suitably m -0.2 to 0.5 (μm), which has the effect of facilitating the deflection of the light beam.

FIG. 14 is a perspective view of a semiconductor laser device provided with a function of controlling optical output. In the figure, reference numeral 18 indicates an FBT source pole for controlling optical output, 19 indicates an FET gate electrode for controlling optical output, and 20 indicates an FIT drain electrode for controlling optical output. In the drawing, a PET for controlling optical output is provided on the left side, and an FgT for optical deflection is provided on the right side. FE for light output control
By controlling the gate voltage of T, the amount of current flowing through the p-type stripe generation region 17 can be changed, so the optical output can be controlled. Similarly, in order to cause the laser to oscillate, the current must be greater than the threshold value.

According to this modification, it only makes light deflection possible.
This also has the effect of being able to control the light output.

According to the present invention, a drive circuit for causing optical deflection can be fabricated on the same substrate on which a semiconductor laser is formed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor laser device for explaining the IjA embedding of the present invention, and FIG. 2 is a box showing the carrier concentration distribution.
Figures 3 to 5 show the relationship between the refractive index distribution and the near-field image and far-field image. FIG. 7 is a perspective view and a cross-sectional view showing this embodiment. FIG. 8 is a diagram showing the carrier distribution in the active layer, and FIG. 9 is a T-line diagram showing the refractive index distribution in the active layer. 10 is a plan view of the device for explaining the traveling direction of light, FIG. 11 is a diagram showing the distribution of light intensity, and FIGS. 12 to 14 are perspective views showing modifications of this embodiment. and a cross-sectional view. 1.8 Active layer 2.3, 7.9 Cladding layer 10 Semi-insulating layer 11 FHTa layer 12 FB'l' source electrode 13 FET gate electrode 14 PwT drain electrode 15 P-side electrode 16 11-side electrode 17 P-type stripe generation Region 17' Second p-type stripe generation region FIG. 1 1↓1↓↓i ~3 ￥] Figure 6 f6 Figure q Figure 8 Figure q Diarrhea 10 Figure 12 Diarrhea! Figure 3

Claims (1)

[Claims] A semiconductor layer having a double heterostructure has an active layer that causes laser oscillation, and first and second cladding layers that have a larger forbidden band width than the active layer and sandwich the active layer. An insulating layer and an FET operation layer are arranged in sequence, a drain and a source are provided in the FET operation layer to constitute an FET, and a stripe-shaped impurity region defining a first current path through which current flows through the laser emission region is formed. 1. A semiconductor light emitting device comprising: a stripe-shaped impurity region defining a second current path in proximity to a first impurity region; and the second impurity region is connected to a source or drain of an FIT.