JPH0563232A - Superluminescent diode - Google Patents

Abstract

PURPOSE:To obtain an SLD element which performs a stable SLD operation even when operating with a high output power. CONSTITUTION:On a substrate 11, provided is a step region 17, which forms an angle in the scope of 0-90 deg. with an optical axis, in the course extending to the rear end face side which is opposed to the end face of emitting a beam. Then, on the substrate 11, formed are in succession a lower clad layer 12, an active layer 13, an upper clad layer 14, and a current blocking layer 15. Further, a Zn-diffused region 16 is formed, and the state of making the active layer 13 interrupted in the step region 17 is generated, and the active layer 13 is made to contact with the lower clad 12 in the step region 17. Since the beam progressing to the rear end face side is bent from the direction of the optical axis by the difference of refractivity between the active layer 13 and the lower clad layer 12, the beam is not returned to the active region, and a laser oscillation is made hard to occur. Therefore, an SLD element, which is operated stably even when operating with a high output power, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super luminescent diode.

[0002]

2. Description of the Related Art In recent years, attention has been paid to a super luminescent diode (SLD) gas which may be positioned between a semiconductor laser and a light emitting diode. This light emitting device has a broad spectrum spread like a light emitting diode and can emit light having a high output comparable to that of a semiconductor laser. Therefore, SL
D has an advantage that high-power and incoherent light can be extracted with good directivity. Utilizing this advantage, the use of a light source for a fiber gyro, etc. is currently being promoted. The structure and manufacturing point of the SLD are how to suppress laser oscillation, widen the spectral width of spontaneous emission light, and increase its optical output.

Hereinafter, referring to FIGS. 2 (a) and 2 (b), the conventional S
The LD will be described. In FIG. 2, 1 is n-GaA
s substrate (hereinafter, simply referred to as a substrate. The same applies when other symbols are repeated), 2 is n-AlGaA
s lower cladding layer, 3 is an undoped AlGaAs active layer,
4 is a p-AlGaAs upper cladding layer, 5 is n-GaAs
The current block layer 6 is a Zn diffusion region. The electrodes are omitted.

Next, the operation will be described. When a voltage is applied in the forward direction to the pn junction of the active layer 3, the current is Z
Only the n diffusion region 6 flows. This is because the current blocking layer 5 and the upper cladding layer 4 are reverse biased with respect to the applied voltage in other places. On the other hand, since the Zn diffusion region 6 is p-type, the reverse bias as described above does not occur. Emission recombination occurs in the active region immediately below the Zn diffusion region 6 to generate light.
In this SLD, in order to suppress laser oscillation, although not shown in the drawing, a non-reflection coating is applied to the emission end face, and the region where the stripe of the Zn diffusion region 6 is interrupted is a current non-injection region in the rear. Since it has a function of absorbing light, effective reflection is reduced and laser oscillation is suppressed.

[0005]

Since the conventional SLD is constructed as described above, when the light output is increased, the absorption in the current non-injection region on the rear surface is saturated and the effective reflectance is increased. However, there is a problem that laser oscillation occurs.

The present invention has been made to solve the above problems, and an object thereof is to obtain an SLD that operates stably in the SLD mode even at high light output.

[0007]

The SLD according to the present invention comprises:
On the way to the rear end face side opposite to the light emission end face,
The crystal layers of the lower clad layer, the active layer, the upper clad layer, and the current brick layer are grown on a substrate provided with a step region forming an angle of 0 to 90 ° with respect to the optical axis, and the thickness of the upper clad layer is increased. The impurity diffusion region is formed so as to partially face in the direction and not reach the step region.

[0008]

In the SLD of the present invention, since the light is refracted in the step region formed in the middle of the substrate, the light does not return to the active region even when reflected by the rear end face, so the effective reflectance is reduced. ,
It does not reach laser oscillation.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 (a) to 1 (c) are views showing an embodiment of an SLD of the present invention, FIG. 1 (a) is a perspective view of a substrate of an SLD before epitaxial growth, and FIG. 1 (b) is a device cross section after epitaxial growth. FIG. 1 (c) is a top view of FIG. 1 (b). In FIG. 1, reference numeral 11 denotes a substrate on which a step region 17 is formed, and the step region 17 is 0 relative to the optical axis on the way to the rear end face side opposite to the light emitting end face on the substrate 11. Formed at an angle of ~ 90 °. Therefore, there is a height difference on the substrate 11 with the step region 17 as a boundary. Reference numeral 12 is a lower clad layer, 13 is an active layer, 14 is an upper clad layer, and 15 is a current blocking layer. Each of these epitaxial layers is formed on the substrate 11 having the height difference, with each step layer 17 as a boundary. The layers are stacked in a state of being displaced in the substrate thickness direction, and the active layer 13 is in a state of being interrupted by the step region 17.

Next, the operation will be described. The difference between the SLD of this embodiment and the SLD of the conventional example is the step region 1
Since it is only whether or not each epitaxial layer is formed on the substrate 11 having No. 7, the description will be focused on this point.

First, the manufacturing method will be described. Figure 1
As shown in (a), the required angle (0
Step regions 17 of 90 °) are formed to make the substrate thickness different. Next, as shown in FIG.
The upper clad layer 12 and the active layer 1 are formed in the same manner as in the conventional example.
3, epitaxial layers of the upper clad layer 14 and the current blocking layer 15 are grown. At this time, the respective epitaxial growth layers are formed in a state of being displaced in the substrate thickness direction with the step region 17 as a boundary. Next, the Zn diffusion region 16 is provided as in the conventional example, but the stripe is formed so as not to reach the step region 17 as shown in FIG. If the angle of the step region 17 is set to, for example, 45 ° with respect to the optical axis, the step region 17 perpendicular to the surface of the substrate 11 is formed in the wet etching.

After the growth of the respective crystal layers as described above, the active layer 13 has a shape such that it is interrupted by the step region 17 and in contact with the lower cladding layer 12, as shown in FIG. Therefore, the light generated in the excitation region and traveling backward is bent at an angle inclined from the optical axis direction due to the difference in the refractive index between the active layer 13 and the lower cladding layer 12. For example, A of the active layer 13
l composition ratio of 0.05, Al composition ratio of the lower cladding layer 12 of 0.1.
In the case of 50, the light travels in the direction deviated from the optical axis by 5 °.

Therefore, as shown in FIG. 1 (c), even if the light is reflected by the rear end face, it does not return to the active layer 13 because it is off the optical axis. Therefore, since the optical amplification due to the reciprocal movement of light on both end faces is not generated normally, a stable SLD can be maintained even during high output operation.

[0014]

As described above, according to the present invention, a step region forming an angle of 0 to 90 ° with respect to the optical axis is formed in the middle of the substrate, and the lower clad is formed on the substrate on which the step region is formed. Layers, an active layer, an upper clad layer and a current blocking layer are formed, and a stripe-shaped impurity diffusion layer is formed which partially faces the thickness direction of the upper clad layer and does not reach the step region. The growth layer is formed so as to deviate in the substrate thickness direction with the step region as a boundary, and the active layer is formed in a state of being interrupted in the step region. Therefore, since the light traveling to the rear end face side is bent from the optical axis direction in the step region, the light from the rear end face does not return to the active layer. Therefore, stable SLD operation can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing steps of an embodiment of a method for manufacturing an SLD of the present invention.

FIG. 2 is a diagram showing a structure of a conventional SLD.

[Explanation of symbols]

 11 substrate 12 lower clad layer 13 active layer 14 upper clad layer 15 current blocking layer 16 Zn diffusion region 17 step region

Claims (1)

[Claims] 1. A substrate provided with a step region forming an angle of 0 to 90 ° with respect to the optical axis on the way to the rear end face side opposite to the light emitting end face, and formed on this substrate. A lower clad layer, an active layer, an upper clad layer, and a current blocking layer, and a stripe-shaped impurity diffusion region that partially faces in the thickness direction of the upper clad layer and does not reach the step region. A super luminescent diode characterized in that.