JPS5988878A - Surface light emitting type light emitting diode - Google Patents

Abstract

PURPOSE:To increase the detected amount of light for monitoring by providing a mechanism to guide light to one or more directions within the surface of an active layer, in a diode of a double hetero structure held between semiconductors having energy gap larger than that of the active layer. CONSTITUTION:By being positioned immediately under a window 29 at the center of an N type InP substrate 21, a V-groove or a mesa groove 31 is formed by chemical etching in the direction of [110], and an N type InGaAsP guide layer 32, the InGaAsP active layer 23, a P type InP layer 24, and a P<+> type InGaAsP cap layer 25 are laminated and epitaxially grown in liquid phase over the entire surface including the groove. At this time, the composition of the layer 32 is so set that the size of the band gap thereof becomes transparent to the emitted light of the layer 23. Since the refractive index of the layer 32 becomes larger than that of the substrate 21 in this manner, the distribution of actual working refractive index is generated in the layer 23 at the time of providing a projection (groove 31 here) on the layer 32 in contact with the layer 23. Therefore, the emitted light is guided to the end surface direction of the diode.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a surface-emitting light emitting diode equipped with a monitor light extraction device.

AlGaAs-GaAs or In1jaAs P-I n
The light emitting diode made of P-based material has an emission wavelength of 0.85 μm.
It is in the vicinity of 1.3 μm, consistent with the low loss of silica yarn optical fibers (°C), and is therefore being put into practical use as a light source for medium and short-distance optical communications and optical information processing.

When a surface light emitting diode is used as a light source for optical communication, a monitor light monitoring device may be required to control the amount of signal light to a constant level. In order to monitor the monitor light, part of the signal light is split with a beam splitter and guided to a photodetector, or part of the reflected light within the stem mounting the light emitting diode is detected. Alternatively, methods have been proposed in which a portion of the light in the direction within the pn junction plane is detected, but these methods have drawbacks such as reducing the amount of important signal light and reducing the amount of light that can be detected. In order to increase the amount of detected light, it is possible to increase the light-receiving area of the detector, but because light-emitting diodes for optical communication are designed to be as small as possible, there is no pace to install a larger detector. The purpose of the present invention was to solve these drawbacks, and the purpose of the present invention was to solve these drawbacks, and to provide a surface-emitting type light emitting diode with a monitor light monitoring device, without attenuating the amount of signal light.
An object of the present invention is to provide a light emitting diode that can increase the amount of light detected for monitoring.

According to the present invention, a mechanism for guiding light in one or more directions within the plane of the active layer is provided in a surface-emitting light emitting diode with a double heterostructure narrowed by a semiconductor having an energy gap larger than that of the active layer. A light emitting diode characterized in that it is provided is obtained.

Although the present invention can be applied regardless of the semiconductor phase material, the case of a double heterostructure surface-emitting light emitting diode made of InGaAsP-InP system, which is attracting attention as a light source for optical communication, will be described in detail below with reference to the drawings. Explain to Milk 1.

FIG. 1 is a conceptual diagram showing an example of a surface-emitting diode with a monitor light monitoring device that has already been proposed.
Signal light 14 from a surface-emitting type light emitting diode 13 mounted on a submount 12 shown at the center of the cap 15 is transmitted to the outside through a window 16 of a cap 15. On the other hand, a monitoring photodetector 17 is placed in one of the areas perpendicular to the direction in which the signal light 14 is taken out so as to be at the same height as the active layer. Figure 2 is a conceptual cross-sectional view showing the basic structure of a surface-emitting type light emitting diode, with n-InP base &21 (1oo)
m, n-1nP buffer layer 22, InGaAs
P active layer 23. p-InP layer 24 and p+-InGaA
The sP cap N25 was grown using a conventional liquid phase continuous growth method. The mixed crystal composition ratio of the active layer 23 is selected in advance so as to have a predetermined wavelength. A p-type partial electrode 26 set to have a predetermined emission diameter is formed on a part of the cap layer 25, and an insulating film 27 such as 5in2 or SiNx is coated around it to limit the emission diameter. I am doing it. n-In
The portion on the P substrate 21 is n except for the portion facing the pole 26.
A flllt pole 28 is formed. Since the n-InP 21 and 22 are transparent to the wavelength of light emitted from the active layer 23, the signal light 14 is extracted to the outside through the window 29 of the n-side electrode. On the other hand, the refractive index of InP 21.22 + 25 is the active layer 23
Since the refractive index of the active layer 23 is smaller than the refractive index of the active layer 23, a part of the light emitted from the active layer 23 is confined in the in-plane direction of the active layer 23 and propagates toward the end surface. Therefore, in the configuration shown in FIG. 1, it is possible to monitor the end face light component. However, since the refractive index of the semiconductor material is large, approximately 3.5, when it exits from the end face, most of it is totally reflected according to the law of refraction, and the amount of light that can be received by the detector 17 is considerably reduced. .

FIG. 3 is a conceptual cross-sectional view showing one embodiment of the present invention.
At the center of the nP group &21, directly below the window 29 [110]
A V-groove or mesa-shaped groove 31 is formed in the direction by chemical etching. On top of that, an n-InGaAsP guide layer 32,
The InGaAsP active layer 23.1)-InP layer 24 and the p+-InGaAsP key'fl bulge layer 25 are grown by a normal five-layer liquid growth method. The composition of the n-InGaAsP guide layer 32 has a band cap size of InG.
The refractive index of the aAsP active layer 230 active layer 2 phantom 032 is n-
Since the refractive index is larger than that of InP 21, when a protrusion (for example, 31) is formed on the guide layer 32 in contact with the active layer 23, the actual dynamic refractive index distribution within the active layer 23 changes depending on the shape of the protrusion. - arise. Therefore, if a V-groove or mesa-shaped groove 31 is formed in the guide layer 32 so as to pass through a limited light emitting part in a surface-emitting type light emitting diode similar to the case explained in FIG. A light waveguide effect occurs in the direction. Therefore, the in-junction surface component of the light emitted by the light emitting part can be efficiently guided toward the end face of the light emitting diode, so that the amount of total reflection at the end face that occurs in FIG. 2 can be drastically reduced. Therefore, in the configuration shown in FIG. 1, the amount of light for monitoring can be increased without attenuating the amount of signal light 14. Therefore, even if the area of the light-receiving portion of the photodetector is reduced to 1/4 s degree of the conventional one, it is now possible to obtain a monitor signal comparable to or greater than that of the conventional one.

Also, considering the mass productivity of the light emitting diode of this invention,
It may be better to form the V-groove or mesa-shaped groove 31 in the (110) direction in both orthogonal directions. In other words, when mounting the light emitting diode 13, which one of the four end faces faces the photodetector 17? Since the above-mentioned effects can be obtained even if the assembly is carried out, the workability during assembly is significantly improved.

(About this invention) Although the surface-emitting light-emitting diode made of InGaAsP active layer P yarn has been described in detail, this invention can be applied to light-emitting diodes made of any other semiconductor material as long as it is a surface-emitting light-emitting diode. Needless to say, it can also be applied to a structure in which the two are replaced.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of a surface-emitting light emitting diode in a conventional monitor light monitoring device, Fig. 2 is a conceptual cross-sectional view showing the basic structure of a conventional surface-emitting light emitting diode, and Fig. 3 is a cross-sectional view showing an example of a surface-emitting light emitting diode. 1 is a conceptual cross-sectional view showing one embodiment of the invention. 11...Stem, 12...Submount, 13...Surface emitting type light emitting diode, ]4
...Signal light, 15 ...Cap, 16
...Glass window, 17...Monitor detector, 21...n-InP substrate, 22...
...n-InP buffer til! , 23...I
nGaAsP active layer, 24... p-InP, 2
5...p''-InGaAsP keep layer, 2
6, 28"""p + n electrode, 27...Insulating film, 29...Light transmission window, 31...V
Groove or mesa-like groove. Figure 1 4 Figure 2 Figure 3

Claims (1)

[Claims] A surface-emitting light emitting diode with a double Peter structure narrowed by a semiconductor having an energy gap larger than that of the active layer, characterized by providing a mechanism for guiding light in one or more directions within the plane of the active layer. light emitting diode.