JPS609187A - Semiconductor light-emitting device - Google Patents

Abstract

PURPOSE:To reduce threshold currents, to improve efficiency and to stabilize a mode by forming a refractive-index guiding to a surface light-emission semiconductor light-emitting device. CONSTITUTION:A P type PbSnTe layer 2 as an active layer and an N type PbTe layer 3 as a second clad layer are grown on a P type PbTe substrate 1 using a (100) face as a main surface in succession. Mesa etching through which an active region is left in a shape such as a circle is executed up to depth reaching to the PbTe substrate 1. An N type PbTe layer 4 and a P type PbTe layer 5 are grown on a surface to be etched in succession, and an N type PbTe layer 6 is grown on the whoel surface. The N type PbTe layer 6 functions as a contact layer for an N side electrode while also serving as a window layer, but the layer 6 grows on the whole surface of a base body when a growth onto the P type PbTe layer 5 progresses and the layer 6 reaches to a growing surface or the height of the upper surface of the N type PbTe layer 3. N side electrodes 7 and a P side electrode 8 are disposed by using a gold group material. The P side electrode 8 functions as one electrode while serving as a reflecting film.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a semiconductor light emitting device, and particularly to a surface emitting semiconductor light emitting device whose characteristics are improved by providing refractive index guiding in its active region.

(b) Technical background Systems that use light as an information signal medium have been developed in a wide range of fields, and semiconductor lasers are often used as light sources for these seven stems.

Semiconductor lasers have the most future potential due to their characteristics such as being able to control the wavelength of the emitted light, being compact and mass-producible, and being easy to use to oscillate with high efficiency just by passing a current through them. Many efforts have been made to improve various properties, such as realizing the required wavelength band and oscillation mode, and increasing efficiency and output.

(C) Prior art and problems As mentioned above, many semiconductor laser structures have been proposed to date, but most of them have FAP IJ-Perot optical resonators arranged in stripes parallel to the semiconductor substrate surface. This is a structure in which the mirror surface is formed between the bones of semiconductor crystals, etc. This end face formation by the interosseous space restricts the shape and dimensions of the laser chip and is an impediment to improving productivity.It also shortens the cavity length, making it difficult to control the axial mode, making it difficult to form integrated circuits including lasers. Make it.

Furthermore, semiconductor lasers with this structure generally have a small light emitting area, which increases the divergence angle of the emitted light, and increases the areal density of the laser light, which promotes deterioration or destruction of the valve opening surface, which reduces reliability. This may result in a reduction in output or a restriction in output.

A surface emitting laser is known as one type of semiconductor laser structure that addresses these problems. A surface-emitting laser is a semiconductor laser that emits laser light in a direction perpendicular to the main surface of a semiconductor substrate, and the -optical resonator usually has a -C configuration in which the surface of an epitaxially grown crystal is used as a reflective surface.

Since the surface emitting laser d has such a structure, (a) it is easy to widen the light emission area, increase the direction of light emission, and narrow the light emission angle. (b) It is easy to shorten the optical resonator length, making it possible to unify the axial mode. Suitable for configurations such as G-9 two-dimensional laser array monolithic optical integrated circuits. It has excellent characteristics such as:

On the other hand, many means have already been provided for the purpose of reducing the threshold current, improving the efficiency, controlling the transverse mode, etc. for the semiconductor laser having the stripe structure parallel to the semiconductor substrate surface mentioned above.

For example, in order to form a striped optical waveguide in the active layer, a cladding layer is provided using a double heterostructure in the vertical direction of the active layer, and in the lateral direction, gain guiding by current concentration is more effective. A large refractive index guiding is achieved by various means such as a buried structure and a difference in impurity doping. By providing refractive index guiding in the lateral direction in this way, transverse mode control is performed, and a single fundamental zero-order transverse mode, deoscillation, etc. are realized.

Regarding current confinement, for example, there is a p
Measures such as providing an n-reverse junction have been taken.

On the other hand, in surface emitting lasers, the lateral guiding of the conventional optical resonator is gain guiding, and there are still many points to be improved, such as insufficient current confinement. The above-mentioned excellent features of the surface emitting laser are features that are desired for future semiconductor lasers, and improvement of the remaining points will have a great effect on the application field of semiconductor lasers.

(a) Purpose of emission ψJ The present invention relates to semiconductor light emitting devices, particularly surface emitting lasers,
The object of the present invention is to provide a structure in which excellent characteristics can be obtained through improvements such as effective light confinement through refractive index guiding.

(0) Structure of the Invention The object of the present invention is to provide a first semiconductor layer of a first conductivity type;
a second semiconductor layer having a larger refractive index and a smaller forbidden band width than the first semiconductor layer, and from which photons are emitted;
A third semiconductor layer having a lower conductivity and a second semiconductor layer having a smaller refractive index and a larger forbidden band width than the semiconductor layer No. are sequentially stacked, and a third semiconductor layer having a smaller refractive index and a larger forbidden band width than the second semiconductor layer. a fourth layer in contact with the side surface where the second semiconductor layer terminates;
the first semiconductor layer of the second semiconductor layer;
Or achieved by a semiconductor light emitting device in which light is emitted in a direction perpendicular to an interface with a third semiconductor layer, in particular, the fourth semiconductor layer has a second conductivity type and is connected to the first semiconductor layer. By providing a fifth semiconductor layer of the first conductivity type on and in contact with the fourth semiconductor layer, a pn junction opposite to this is formed around one light emitting region, and current confinement is performed.

In the semiconductor light emitting device of the present invention, selective etching is performed on a semiconductor substrate on which an active layer, a cladding layer, etc. are epitaxially grown, leaving an active region in a mesa shape, and a confining effect is produced on the surface formed by this etching. It can be easily manufactured by growing a semiconductor layer having the following properties.

In particular, lead telluride (PbTo), lead tin telluride (PbSn)
For many semiconductor materials such as Te), when the main surface of the semiconductor substrate is the (100') plane and the semiconductor layer is grown by the liquid phase epitaxial growth method after mesa etching, the plane orientation of the substrate crystal at this semiconductor layer growth rate is Dependencies on are used effectively.

(f) Embodiments of the Invention The present invention will now be described in detail from embodiment t' with reference to the drawings. Figures 1 to 4 show wavelength numbers [μm] to 20
[μm'J Hodoka's infrared semiconductor laser: This embodiment of the present invention is a sectional view showing the state of the main manufacturing process.

Refer to Fig. 1. A p-type Pb5nTe layer 2 with a (100) plane as its main surface as a main surface is formed on the b Te substrate 1 to a thickness of, for example, about 1 to 2 [μm], and a second 's Kushinodotsuru n
The thickness of the type PbTe layer 3 is, for example, about 2 [μJrI].

Sequential liquid phase epitaxial growth method 1) 1) Growth is performed.

Refer to Figure 2. PbTe
This etching process is carried out to a depth of l″c′c′ reaching the substrate 1.
This can be carried out using an etching solution added to a certain degree.

Referring to FIG. 3, by a liquid phase epitaxial growth method, an n-type PbTe layer 4+p-type PbTe layer 5 are sequentially grown on the etched surface, and an n-type PbTe layer 6 is further grown on the entire surface. n-type Pb
The Te layer 4 is grown in contact with the side surface where the Pb5nTe active layer 2 terminates, and has a refractive index of about 6.2 to 6.5.
Since the refractive index of the 5nTe active layer 2 is as low as about 6.0, the Pb5nTe active layer 2 and the PbTe substrate 1 or the Pb
The heterogeneity with the Te cladding layer 3 is 1. The refractive index is daddy for light in the direction perpendicular to the junction interface.
e from the second cladding layer 3 through the Pb5nTθ active layer 2
fflPbTθ forms a reverse junction for the current to the substrate IK1, thereby confining the current.

The growth of the n-type PbTe layer 4 and the n-type PbTe layer 5 described above is due to the dependence on the crystal orientation of the substrate during liquid phase epitaxial growth, as described above.

This process can be carried out without growing on the upper surface of the PbTθ second cladding layer 3, which is a (100) plane.

The n-type PbTe layer is a contact layer for the 6idn side electrode as well as a window layer, but if the growth on the p-type PbTe layer 5 progresses and the growth surface reaches the height of the upper layer of the n-type PbTe layer 3, The growth takes place over the entire surface of the substrate.

Refer to FIG. 4, the ngR electrode 7 and the p-side electrode 8 are provided using a gold (Au-based material). However, in this embodiment, the n-type PbTe layer 6
The upper n-side electrode 7 is provided with a light exit port, and Pb
The p-side electrode 8 on the Te substrate 1 is formed by etching the substrate 1 from the back surface at a position corresponding to the active region so that the thickness of this part is about 100 [μm] or less, about 30 to 50 [μm]. are installed as shown in the figure. This p-side electrode 8 is one electrode and also functions as a reflective film.

The semiconductor light emitting device according to the present invention can be manufactured by the manufacturing method as explained above. In the light emitting device according to the present invention, the active layer is completely surrounded by a semiconductor layer having a smaller refractive index and a larger forbidden band width than the active layer.
Light generated in the active layer resonates in a direction perpendicular to the main surface of the substrate, and since refractive index guiding is provided on the side surface of the active layer, light is effectively confined in this direction. In addition, as in this embodiment, current confinement is possible by providing a pl'l reverse junction, and furthermore, it is possible to use one electrode as a metal reflective surface of the optical resonator, so that the threshold current can be lowered. The efficiency can be high and the mode can be stabilized.2 Although the above-described embodiments are directed to long-wavelength infrared lasers,8 the present invention can also be applied to surface-emitting semiconductor light-emitting devices using different semiconductor materials. I can do it.

(gl) As described in detail, according to the present invention, refractive index guiding can be easily and effectively provided in a single surface emitting semiconductor light emitting device, thereby reducing threshold current, improving efficiency, stabilizing the mode, etc.
A surface-emitting semiconductor light-emitting device with improved % performance is provided.

[Brief explanation of drawings]

FIGS. 1 to 4 show embodiments of the present invention. FIG. 3 is a cross-sectional view showing the state in the main manufacturing process. In the figure, 1 is a p-type PbTe substrate, 2 is a p-type Pb5n
Te active layer, 3 is n-type PbTe layer, 4 is n-type PbTe layer, 5 is p-type pbTe/1.6 is n-type P 'b Te layer 7 &:l: n-side electrode, 8 is p-side electrode shows. Potato 1 Kute 2 Diagram

Claims (2)

[Claims] (1) A first semiconductor layer of a first conductivity type, a second semiconductor layer having a larger refractive index and a smaller forbidden band width than the first semiconductor layer and emitting photons, and the second semiconductor layer. The third layer of the second conductivity type has a smaller refractive index and a larger forbidden band width than the third layer.
semiconductor layers are sequentially stacked and have a smaller refractive index and a larger forbidden band width than the second semiconductor layer;
A fourth semiconductor layer is provided in contact with a side surface where the semiconductor layer terminates, and light is emitted in a direction perpendicular to the interface between the second semiconductor layer and the first or third semiconductor layer. Semiconductor light emitting device. (2) The fourth semiconductor layer has a second conductivity type and is in contact with the first semiconductor layer, and a fifth semiconductor layer of the first conductivity type is provided on the fourth semiconductor layer. A semiconductor light emitting device according to claim 1, characterized in that: