JPH04139772A - End surface light emitting diode - Google Patents

Abstract

PURPOSE:To improve absorption efficiency by arranging, in the rear part, a region in which at least an active layer is formed as the same layer as a light emitting part, and turning said region to a non-excitation region, by applying an electric field to said region, in the direction opposite to the light emitting part. CONSTITUTION:A front region functions as a light emitting diode. That is, by applying a voltage across a P electrode 11 and an N electrode 23, an active layer 17 is excited and generates light. A light oozing backward from the excited region of the layer 17 is absorbed by an active layer 18 in the rear part, via a non-waveguide region. Electron-hole pairs generated as the result of light absorption are led out as a current by a backward bias voltage applied across the P electrode 11 and the N electrode 24. Thereby the electron-hole pairs generated as the result of light absorption can be rapidly diffused, saturation level is raised, and absorption efficiency in the light absorption region is improved, so that reflected light can be decreased.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to light emitting diodes, particularly optical communication and information processing,
The present invention also relates to edge-emitting diodes in the field of measurement and the like.

(Prior art) Suppressing laser oscillation and reducing temperature dependence at low temperatures are the most important issues in edge-emitting diodes. Various measures are being taken.

FIG. 3 shows an example of an edge light emitting diode in which a non-waveguide region is provided behind a light emitting portion, and a portion thereof is cut away to illustrate the inside. In the figure, 30 is n
31 is an n-InP substrate, 32 is an n-InP buffer layer, 33 is an active layer of n-GaAsP, and 34 is a p-
35 is a p-InGaASP contact layer, 36 is a p-InP block layer, 37 is an n-
InP block layer, 38 is n-InGaAsP layer, 3
9 is a p-electrode. The p-InP block layer 36 and the n-InP block layer 37 at the rear of the InGaAsP active layer 33 become non-waveguide regions, and the excitation light propagated backward from the InGaAsP active layer 33 is spread and emitted from the rear. be done.

FIG. 4 is a partially cutaway perspective view of a conventional edge-emitting diode in which a non-excited absorption region for suppressing laser oscillation is provided in the rear portion.

In the figure, 41 is a p-electrode, 42 is a p-InP substrate, 43 is an n-InP block layer, 44 is a p-In-P block layer, 45.46 is a p-InP cladding layer, 47, 4
8 is an active layer of InGaAsP, 49 is a cladding layer of n-InP, 50 is a contact layer of n-InGaAsP, 5
1 is an n-electrode, and 52 is a 5in2 insulating layer. p-In
P cladding layer 45,46 and InGaAsP active layer 4
7° 48 is formed simultaneously before and after the buried region, and the active layer 47 in the front is formed by the n-electrode 41 and the n-electrode 51.
The front side constitutes a light emitting diode because it becomes an excitation region that is excited by the current flowing between the two. No current flows through the rear active layer 48, and this portion becomes a non-excited absorption region. An n-InP block layer 43 existing in between
The block layer 44 of p-InP forms a non-waveguide region, and transmits light from the excitation region of the active layer backward to the light absorption region of the active layer while diffusing it. Therefore, light leaking backward from the excitation region of the active layer is absorbed by the light absorption region, and oscillation can be prevented.

However, in such conventional edge-emitting diodes, in order to sufficiently absorb the light leaking backward from the excitation region of the active layer, it is necessary to increase the length of the light absorption region. There is a problem that the element size becomes large.

Additionally, edge-emitting diodes have problems with their temperature characteristics. FIG. 5 shows an example of the temperature characteristics of an edge-emitting diode, with the horizontal axis representing the case temperature and the vertical axis representing the relative light output. As can be seen from the figure, the temperature dependence is particularly large in the low temperature region, reaching around 3%/℃ near 0°C.
This value is extremely large compared to the temperature dependence of light output of a normal surface-emitting diode, which is about 0.5%/°C.

As a countermeasure for this, automatic light output control may be considered, but as explained in Figures 3 and 4, there is a non-excitation region and a non-waveguide region behind the excitation region, so Light seeping backward from the excitation region of the layer is absorbed here and spread out again, so that the intensity of the light emerging from the rear end face becomes very weak.

Therefore, it is difficult to monitor the rear emitted light with a photodiode and control the output.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, and is capable of sufficiently absorbing light leaking backward from the active layer with a simple configuration. The object of the present invention is to provide an edge light emitting diode whose output can be easily monitored.

(Means for Solving the Problems) The present invention provides an edge-emitting diode with a region in which at least the active layer is formed as the same layer as the light-emitting portion in the rear portion, and applies an electric field in the opposite direction to the light-emitting portion to the region. It is characterized in that it is a non-excited region.

(Function) The present invention provides an edge light emitting diode in which a region in which at least the active layer is formed as the same layer as the light emitting portion is provided in the rear portion, and an electric field is applied to the region in the opposite direction to that of the light emitting portion to excite the non-excited region. By doing so, the saturation level of the active layer in the rear region can be increased, and the absorption efficiency can be improved.

Furthermore, the non-excited region formed in the rear portion can function as a light receiving element, and the optical power of the edge light emitting diode can be monitored.

(Embodiment) FIG. 1 is a perspective view of an embodiment of the edge light emitting diode of the present invention. A part of the figure is cut away for explanation. In the figure, 11 is an n-electrode, 12 is a p-InP substrate, and 13 is an n-electrode.
-InP block layer, 14 is p-InP block layer, 15.16 is p-InP cladding layer, 17, 18 is InGaAsP active layer, 19.20 is n-InP cladding layer, 21.22 is A contact layer of n-InGaAsP, 23 and 24 are n electrodes, and 25 is a 5in2 insulating layer.

A method for manufacturing the edge light emitting diode shown in FIG. 1 will be explained with reference to FIG.

■ As shown in Figure 2 (A), the p-InP substrate 12
, an n-InP block layer 13, and a p-InP block layer 14 are sequentially crystal-grown. Through this first crystal growth, a current blocking layer can be formed on the substrate.

Liquid phase epitaxial growth (LPE) is the most common crystal growth method, but vapor phase epitaxial growth (VPE, M
An appropriate method such as an OCVD method can be used.

■ A film of SiO2 is deposited on top of it as an etching mask, and as shown in Figure 2 (B), after removing 5 in2 of the part where the buried trench will be formed using photolithography, a hydrochloric acid-based etching solution is used to remove the area. to form a V-groove, and remove 5102.

■ Next, a second crystal growth is performed, and the V formed
In the groove, p-InP cladding layers 15 and 16, InGa
On the AsP active layers 17 and 18, n-In
P cladding layers 19 and 20 and n-InGaAsP contact layers 21 and 22 are formed.

■ In the central non-embedded area where the V-groove was not formed,
As shown in FIG. 2(C), grooves are formed to electrically cover the front and rear buried regions.

The groove is cut so as to reach the p-InP block layer 14 formed in the first crystal growth.

(2) After depositing 5in2 on the entire surface and filling the groove, remove the SiO□ on the front and rear parts, leaving the S102 insulating layer 25 formed in the groove in (2).

■ Over the entire surface, e.g. T i / P
t/A u electrode metal on the back side, A u Z n
After depositing the electrode metal of /Cr/Au, the electrode metal on the 5in2 insulating layer is removed to form n-electrodes 23, 24 and n-electrode 11.

(2) Finally, an anti-reflection film (not shown) is formed on both sides of each element from the wafer, completing the edge-emitting diode shown in FIG.

The operation will be explained.

The front area acts as a light emitting diode.

That is, the voltage applied between the n-electrode 11 and the n-electrode 23 excites the InGaAsP active layer 17 to emit light. The light leaking backward from the excitation region of the active layer passes through the non-waveguide region to the active layer 1 of InGaAsP at the rear.
Absorbed at 8. Electron-hole pairs generated by light absorption are extracted as a current by a reverse bias voltage applied between the n-electrode 11 and the n-electrode 24.

Therefore, electron-hole pairs generated by absorption of light can be quickly diffused, the saturation level is increased, and the absorption efficiency in the light absorption region is improved, so that reflected light can be further reduced.

In addition, this current can be used as a monitor of the light emission intensity in the light emitting part, and by using it as an input terminal of an automatic output control circuit, it is possible to guarantee output fluctuations due to temperature changes and obtain stable light output. can.

In addition, although the above-mentioned embodiment explained the case where a p-type substrate was used, it goes without saying that an n-type substrate can be used. Further, the present invention is applicable not only to InGaASP type but also to other types.

(Effects of the Invention) As is clear from the above description, the present invention has the effect of providing an edge-emitting diode that can sufficiently suppress laser oscillation and perform automatic output control.

Furthermore, since the light emitting element portion and the light receiving element portion are formed on one substrate, there is no need to align the two, and there is an advantage that mounting can be simplified.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view for explaining an embodiment of the edge light emitting diode of the present invention, FIG. 2 is an explanatory diagram of the manufacturing process of the edge light emitting diode of FIG. 1,
3 and 4 are partially cutaway perspective views of a conventional edge light emitting diode, and FIG. 5 is a diagram showing the temperature characteristics of the edge light emitting diode. 11... Electrode, 12... Substrate, 13.14... Block layer, 15.16... Clad layer, 17.18...
...Active layer, 19.20...Clad layer, 21,22
... contact layer, 23, 24... n electrode, 25.
...Insulating layer. Patent applicant: Shimadzu Corporation

Claims (1)

[Claims] An end face of an edge light emitting diode, characterized in that a region in which at least the active layer is formed as the same layer as the light emitting part is provided in the rear part, and an electric field in a direction opposite to that of the light emitting part is applied to the region to make it a non-excited region. light emitting diode.