KR960002647B1 - The structure of semiconductor laser diode - Google Patents

Abstract

The laser diode includes a substrate (1) with a buffer layer (2) formed on top, a clad layer (3) formed on the intermediate layer, an active layer (4) formed on the clad layer, another clad layer (5) formed on the active layer, intermediate layers (10, 20) formed on the latter clad layer, a current limiting layer(6) and a cap layer (7) formed on the intermediate layers in turn, and a metal electrode(9) formed thereon. The intermediate layer has an energy band gap larger than that of the substrate and smaller than that of the initial clad layer. The intermediate layer is also of the same material as the initial clad layer, but with a different composition. The intermediate layer has a multi-layered structure including a number of layers having different energy band gaps. Intermediate layer reduces series resistance component and makes flow of current smooth. Heat generation is reduced enabling increased output.

Description

Structure of Semiconductor Laser Diode

1 is a cross-sectional view showing the structure of a conventional semiconductor laser diode.

2 is a cross-sectional view showing the structure of the semiconductor laser diode of the present invention.

3 is a cross-sectional view showing the structure of the semiconductor laser diode of the present invention.

4 is an energy band characteristic diagram of a laser diode.

* Explanation of symbols for main parts of the drawings

1,11 substrate 2,12 buffer layer

3,5,13,15 cladding layer 4,14 active layer

6,16 current limiting layer 7,17 cap layer

8,9,18,19 metal electrode 10,20 intermediate layer

The present invention relates to a structure of a semiconductor laser diode, and more particularly, to lowering the series resistance component of the laser diode to enable operation at low current.

In the conventional semiconductor laser diode, the buffer layer 12, the first conductive cladding layer 13, the active layer 14, the second conductive cladding layer 15, and the current limiting the substrate 11 on the substrate 11 as shown in FIG. The layer 16 and the cap layer 17 are sequentially grown, and the first conductive metal electrode 18 and the second conductive metal electrode 19 are grown on the substrate 11 and the cap layer 17. Was done.

In the conventional laser diode as described above, the current from the second conductive metal electrode 19 is limited to a narrow region by the current limiting layer 16 through the cap layer 17, and thus the second conductive clad has a high current density per unit area. The current flows into the layer 15, and the current is recombined in the active layer 14 to the first conductive metal electrode 18 through the first conductive cladding layer 13, the buffer layer 12, and the substrate 11. Flows out.

In the above, the size of the energy gap of the active layer 14 is smaller than that of both the cladding layers 13 and 14, the refractive index is large, and electron holes are collected in the active layer, and the generated light is connected to the active layer 14 by refraction. The oscillation start current is lowered. In addition, the buffer layer 12 buffers crystal defects and the like of the substrate 11 to obtain higher quality crystal layers.

However, such a conventional semiconductor laser diode has a large energy gap difference between the cap layer 17 and the second clad layer 15 or the substrate 11 (or the buffer layer) and the first clad layer 13 when a current is injected. . Therefore, the flow of current feels a barrier caused by the energy band difference, so that a resistance component is generated, thereby generating heat, thereby deteriorating the electro-optical characteristics of the device.

In addition, the energy band has a spike-like high barrier formed at the interface between the cap layer 17 and the cladding layers 13 and 15, the cladding layers 13 and 15, and the substrate 11. Able to know. Due to this barrier, the flow of electrons and holes is restricted and parasitic resistance components generate heat. Therefore, the operating current is increased to generate heat and to decrease the reliability and to accompany unwanted phenomena such as change in wavelength of emitted light by heat.

Accordingly, an object of the present invention is to reduce the series resistance component by inserting an intermediate layer between the cladding layer and the current limiting layer to enable operation at low current.

According to the present invention having the above object, a single layer or a multi-layer intermediate layer having a small energy gap and a larger energy cap than a cap layer of a buffer layer, a first conductive clad layer, an active layer, and a second conductive clad layer is formed on the substrate. To grow.

The current limiting layer and the cap layer are grown on the intermediate layer, and then the first and second conductive metal electrodes are deposited on the substrate and the cap layer.

2 will be described in detail with reference to the accompanying drawings.

The buffer layer 2, the first conductive cladding layer 3, the active layer 4, and the second conductive cladding layer 5 are grown on the substrate 1. The first intermediate layer 10 and the second intermediate layer 20 are grown on the second conductive clad layer 5, and then the current limiting layer 6 and the cap layer 7 are grown.

The first conductive metal electrode 8 is deposited on the substrate 1, and the second conductive metal electrode 9 is deposited on the cap layer 7.

In the above, the intermediate layers 10 and 20 have a larger energy gap than the clad layer 5 and a smaller energy gap than the cap layer 7.

3 is a perspective view showing the whole of the semiconductor laser diode manufactured as described above.

4 shows energy band characteristics of a laser diode.

Reference numeral L denotes a conductor.

The working effect of the laser diode of the present invention prepared as described above will be described.

The current flowing into the metal electrode 9 through the conductive line L is transferred from the active layer 4 through the cap layer 7, the second and first intermediate layers 20 and 10, and the second conductive clad layer 5. The light is recombined and flows through the first conductive clad layer 3, the buffer layer 2, and the substrate 1 to the first conductive metal electrode 8.

The role of the first and second intermediate layers 10 and 20 in this case is that current flows from the cap layer 7 to the second conductive cladding layer 5 or from the substrate 1 to the first conductive cladding layer 3. As it reduces the barrier caused by the energy band discontinuity level, the current flows smoothly.

4 is a diagram showing the change in the energy band of the barrier formed at the interface between two layers having different energy band caps, and the clad material having a large energy band gap from the cap layer 7 or the substrate 1, which is a material having a small energy band gap. When current flows into layers 3 and 5, a spike-like barrier is encountered at the interface. This spiked barrier hinders the flow of current and exhibits resistive components that generate heat.

Since the spike barrier is proportional to the difference between the energy gaps of the two materials, the spike type is abruptly because the first and second intermediate layers 10 and 20 having an intermediate energy gap between the two materials are inserted in the present invention. This reduces the current flow smoothly.

As described above, the semiconductor laser diode of the present invention enables low current operation by inserting an intermediate layer to reduce the series resistance component, thereby reducing heat generation during operation to obtain high output, and reducing current spike barriers of energy band gap differences. This makes it possible to provide a laser diode device with low current operation and high reliability.

Claims (3)

A buffer layer, a first conductive clad layer, and an active layer second conductive clad layer are formed on the substrate, and an intermediate layer having a smaller energy gap than the clad layer and a larger energy gap than the cap layer is formed on the second conductive clad layer. The current limiting layer and the cap layer are sequentially formed on the intermediate layer, the structure of the semiconductor laser diode, characterized in that the structure consisting of a metal electrode deposited on the substrate and the cap layer. The structure of a semiconductor laser diode according to claim 1, wherein the intermediate layer has a multilayer structure having several different energy gaps. The structure of a semiconductor laser diode according to claim 1 or 2, wherein the intermediate layer has a structure such that an energy gap becomes smaller from the clad layer side toward the cap layer side.