JPH0277174A - End face radiation type light emitting diode - Google Patents

Abstract

PURPOSE:To actuate stably the title diode at low temperature and without causing an oscillation by a method wherein a nonexcitation absorption region consisting of a compound semiconductor having an energy band gap smaller than that of an active layer is provided in the vicinity of the end face on one side of an optical waveguide. CONSTITUTION:A nonexcitation absorption region consisting of a P-type InP layer 9, a non-doped InGaAs photo absorption layer 10 having an energy band gap of 0.75eV, an N-type InGaAsP antimeltback layer 11 and an N-type InP layer 12 is provided in the vicinity of the end face on one side of an optical waveguide. The energy band gap of this layer 10 is smaller than that of an optical waveguide layer (an active layer) 3. Moreover, the thickness of the layer 10 is formed thicker sufficiently than that of the layer 3 and the width of the layer 3 is formed wider sufficiently than that of the layer 10. That is, as the energy band gap in the composition of the nonexcitation absorption region is smaller than that in the composition of the active layer, a ratio that light generated in the active layer (the optical waveguide layer) is absorbed is high and the amount of the light to reach up to the end face of the element is significantly decreased and an oscillation can be inhibited.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Application Field) The present invention relates to an edge-emitting light emitting diode that extracts spontaneously emitted light from the end face of an optical waveguide as optical output, and in particular, The present invention relates to an edge-emitting type light emitting diode in which Fabry-Perot oscillation is sufficiently suppressed by reducing the rate.

(Prior Art) Compared to an end face tli injection valve type light emitting diode, the reflected return light does not affect the optical output, and the light output is excellent in reliability and inexpensive.

Additionally, compared to surface-emitting light-emitting diodes, it has excellent coupling to single-mode fibers, and is used as a light source for large-capacity communications and fiber gyros.

In a semiconductor device equipped with a striped optical waveguide, light reflection occurs at the end face of the optical waveguide.

A Fabry-Perot laser diode effectively utilizes light reflection at this end face. On the contrary,
Edge-emitting light emitting diodes, on the other hand, dislike this edge reflection in order to take advantage of their original characteristic of spontaneous emission. That is, as the temperature decreases, the stimulated emission light increases, and the ratio of the stimulated emission light to the spontaneous emission light increases, resulting in a significant decrease in reliability.

Conventionally, various structures have been proposed to suppress the anti-q1 at the end face.

(1) Provide a non-reflective film on the end face.

(2) Form the end face obliquely.

(3) Provide a window structure near the end face.

(4) An insulating layer is provided opposite the active layer near the end face, that is, the optical waveguide layer, to form a so-called non-excited absorption region in which no current is injected into the optical waveguide layer.

(5) A non-excited absorption region and a window structure are provided near the end face.

(Problems to be solved by the invention) In the above (1), it is necessary to control the thickness of the non-reflective film to the order of 100 angstroms, and it cannot be formed with good reproducibility using a CD device or an electron beam evaporation device. It is not suitable for mass production.

The essence of (2) is to suppress co-photography by causing the reflected light at the end face to escape from the optical waveguide, but a large amount of light remains in the optical waveguide, causing Fabry-Perot excavation at low temperatures.

In (3), when the length of the window region is set to about 200 am, the effective reflectance decreases to 1%, but even if it is made longer than that, the window region of the element itself becomes an optical waveguide, and the effective reflectance does not change. First, Fabry-Bello oscillation occurs at low temperatures.

(4) suppresses stimulated emission by reducing the amount of light that contributes to the anti-QJ at the end facets. is 70
An unexcited absorption region with a length of 0-100 μm is required. In order to prevent oscillation even at low temperatures, a longer non-excited absorption region is required, which reduces the number of devices cut out from a single wafer and makes it difficult to mount the devices.

Even in the case of (5), in order to prevent oscillation at low temperatures, a long region is required in the window region M and the σ unexcited absorption region. This reduces the number of elements that can be mounted, and also makes it difficult to mount the elements.

As described above, with the conventional techniques, it has not been possible to obtain an edge-emitting light-emitting diode that operates stably at low temperatures without causing excavation and is excellent in mass production.

The present invention provides an edge-emitting light emitting diode that operates stably at low temperatures without causing oscillation and is highly suitable for mass production.

[Structure of the Invention] (Means for Solving the Problem) The invention according to claim 1 provides an edge-emitting light emitting device in which an active layer that generates light forms a striped optical waveguide, and the spontaneously emitted light is extracted from the end face. This is an edge-emitting 1llFl type light emitting diode characterized in that an unexcited absorption region made of a compound semiconductor having a smaller energy bandgap than an active layer is provided near the end face of an optical waveguide.

The invention according to claim 2 is an edge-emitting light emitting diode that extracts spontaneously emitted light from an end face of a striped active layer that generates light, characterized in that an unexcited absorption region having a scattering surface is provided near the end face. This is an edge-emitting light emitting diode.

(Function) In the edge-cutting type light emitting diode according to claim 1, since the composition of the unexcited absorption region has a smaller energy band gap than the composition of the active layer, light generated in the active layer (optical waveguide layer) is absorbed. The light transmission rate is high, and the amount of light reaching the element end face is significantly reduced, making it possible to suppress oscillation. Moreover, since the rate of absorption of light generated in the active layer is high and there is no need to form a long non-excited absorption region, the size can be made smaller compared to conventional technology, and many devices can be produced from a single wafer. suitable for

In the edge-emitting IJJ type light emitting diode according to claim 2, since the non-excited absorption region has a scattering surface, most of the light that has propagated in the wave path in the past is scattered, making it difficult for Fabry-Perot excavation to occur, and causing the non-excited absorption region to scatter. Since it does not need to be formed long, it can be made smaller than conventional techniques, and more elements can be taken out from one wafer, making it suitable for mass production.

(Example 1) Hereinafter, an edge molded light emitting diode according to a first example of the present invention will be described in detail with reference to FIGS. 1 to 4.

FIG. 1 is a longitudinal cross-sectional view of an edge molded light emitting diode according to an embodiment of the present invention, FIG. 2 is a cross-sectional view, FIG. 3 is a partially cutaway perspective view, and FIG. 4 is a diagram showing characteristics. It is.

The edge-emitting light-emitting diode of this embodiment has n-1n on a single-crystal substrate 1nP1 of a compound made of ■-V group elements.
A striped laminate consisting of a p-variety layer 2, an energy band of %"l sp 0.94 eV, an lnGaASP optical waveguide layer (active layer) 3, a p-1nP cladding layer 4, and a p-InGaΔSp contact layer 5 is provided. p-1nP layer 6, n-1nP layer 7 and n-1nP layer 6 on both sides.
- a current blocking layer consisting of an InGaAsP layer 8 is provided;
A striped stack is embedded with a current blocking layer.

Then, near one end face, there is p-InF3, non-doped InGaA with an energy band gap of 0.756V.
S light absorption layer 10. An unexcited absorption region consisting of n-In nGaASP angel melt pack layer 11 and n-In pH2 is provided. This light absorption layer 10 has an energy bandgap smaller than that of the optical waveguide layer 3 . Further, the thickness of the light absorption layer 10 is the same as that of the optical waveguide layer 3.
It is formed to be sufficiently thicker than the thickness of the optical waveguide layer 10, and its width is sufficiently wider than the width of the optical waveguide layer 10. In the example, the active layer (optical waveguide layer) 3 has a width of 2.5 μm and a thickness of 0.3 μm.
μrT1, length 250 μm, and light absorption layer 10 width 40 μm
The thickness was 0 μm, the thickness was 2 μm, and the length was 400 μm.

Then, n-1nl) the ground surface of substrate 1 and C1-InGa
The surface of the ASP contact layer 5 is provided with a layered surface 3.14.

Next, a method of manufacturing this edge-radial type light emitting diode A will be explained.

First, a single crystal substrate 1nP of a compound consisting of m-v group elements.
1, n-1nP buffer layer 2, InGaASP optical waveguide layer (active layer) 3 with an energy band gap of 0.94 eV, E)-InP cladding layer 4, p-I nGaAS
The Pj contact layer 5 is grown in this order by liquid phase epitaxial growth (
LPE) method.

Next, stripe-shaped silicon dioxide (
(not shown), and then use this as a mask to coat Br-
The InP substrate 1 is etched by anisotropic etching using the CH30H solution and the (C+-1-(3PO4) solution until the InP substrate 1 is exposed. As a result, the n-1nP buffer layer 2
, InGaASP optical waveguide layer (active t layer) 3, I)-1
An nP cladding layer 4 and a p-I nGaAsP:] contact layer 5 are formed in a stripe shape.

After this, p-I
nP layer 6, n-Inp layer 7 and n-InGaAsP
Layers 8 are successively formed by LPE to provide a current blocking layer.

Next, the striped silicon dioxide is removed and the entire surface is coated with silicon dioxide again. Thereafter, the silicon dioxide in the portion that will become the non-excited absorption region is removed, and using the remaining silicon dioxide as a mask, etching is performed using a hydrochloric acid-based or sulfuric acid-based edger until the InP substrate 1 is exposed. After this, again 1)-
InF3, non-doped nGaAs light absorption layer 10 with an energy band gap of 0.75 eV. n-I nGaA
The SP anti-meltback layer 11 and the n-Inp layer 12 are grown and coated in this order by the LPE method to form a non-excited absorption region.

Next, the silicon dioxide is removed, and the ground surface of the n-1nP substrate 1 and the surfaces of the p-1nGaASP contacts 1 to 5 are coated with a conductive metal layer to form electrodes 13 and 14. Thereafter, the edge-emitting light emitting diode is opened so that the active layer length and light absorption layer length are as described above.

In the edge molded light emitting diode of the present invention described above, the composition of the non-excited absorption region has a smaller energy band gap than the composition of the active layer, so the proportion of light generated in the active layer (optical waveguide layer) is absorbed. is high, the distance between light reaching the element end face is greatly reduced, and excavation can be suppressed.

FIG. 4a shows the change in the spectral half-width of the edge-emitting light emitting diode of this example in the temperature range of -40°C to 60'C. Example of wheezing release! In the 7-1 type light emitting diode, a linear change that depends only on the temperature change in the energy bandgap of the active layer is seen, indicating that it operates stably even at a low temperature of -40°C.

Figure 4 shows the temperature changes in the spectral half-width of 1q for an element with only a #4 window structure and an element with only an unexcited absorption region of the same composition as the active layer, respectively.
Shown in c. As is clear from Figures 4 and 4c, in the edge-emitting light emitting diode of the comparative example, at a low temperature of -40'C, there was a sudden decrease in the half-width of the spectrum from the previous linear change. It shows.

In the above embodiment, the thickness of the absorption layer of the non-excited absorption region is sufficiently thicker than the thickness of the optical waveguide layer, and the thickness of the absorption layer is sufficiently wider than the width of the optical waveguide layer. Since the cross-sectional area of the optical waveguide is made larger than the cross-sectional area of the optical waveguide, this unexcited absorption region also has the effect of a window region. In other words, the light that enters the non-excited absorption region from the optical waveguide spreads radially, and as a result, the efficiency with which the reflected light from the element end face is coupled back into the optical waveguide decreases, and the effective reflectance is drastically reduced, causing oscillation. It has a suppressive effect. This allows the device to be made more compact.

Furthermore, in the above embodiment, a pn reverse junction was formed in order to prevent current from being injected into the non-excited absorption region.
However, the invention is not limited to this, and for example, an insulating layer such as silicon dioxide may be provided under the electrode 14 in a portion facing the region provided with the light absorption layer to form a non-excited absorption region.

(Example 2) FIG. 5 is a cross-sectional view of an edge-emitting light emitting diode according to another embodiment of the present invention, FIG. 6 is a partially cutaway perspective view, and FIG.
The figure is a diagram showing characteristics.

The face-emitting light emitting diode of this embodiment has a light emission center at 1.3 μm, and as shown in FIGS. 5 and 6, an In
A diffraction grating 21 with a period of 6000 angstroms is provided on the surface of the P substrate 20 with a width of 500 μin.
nGaAsP guide layer 22, InGaASP active layer and absorption layer 24, D-1nP cladding layer 26, p-I nG
The aAsP-1 contact layers 28 are sequentially laminated. This laminated body is etched into a stripe shape, and on both sides there is a p-1nP layer 32 which becomes a current blocking layer, and an n-
A 1np layer 34 and an n-1rlGaAsP layer 36 are formed and the striped stack is embedded.

In the region 30, which is the unexcited absorption region, p-1nG
aASPl contact layer 28 and n-1nQaAsP layer 3
A silicon dioxide layer 38 is provided on top of the device 6, and the top and bottom surfaces of the device are further coated with a conductive metal layer and provided with electrodes 40,41.

In this embodiment, a diffraction grating that is distant from the phase matching condition for the emission wavelength is used as the scattering surface, so that almost no light is returned or reflected by the diffraction grating, and most of the light becomes scattered light. Note that the scattering surface is not limited to a diffraction grating.

FIG. 7 shows the change in the spectral half-value width of the edge-emitting light emitting diode of this example in the temperature range of 140° C. to 60° C. In the edge-emitting light-emitting diode of the example, a linear change in the energy bandgap of the active layer that depends on the change in temperature of the emitting-type light-emitting diode is observed.
It can be seen that it operates stably even at a low temperature of -40'C.

[Effects of the Invention] The edge molded light emitting diode of the present invention operates stably at low temperatures, is highly reliable, is easy to control, and improves reproducibility, resulting in a very high yield. is obtained. Moreover, it is small and a large number of elements can be obtained from a single wafer.
Can be manufactured cheaply.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an edge-emitting light emitting diode according to an embodiment of the present invention, FIG. 2 is a cross-sectional view thereof, FIG. 3 is a partially cutaway perspective view, and FIG. 4 is a diagram showing characteristics. FIG. 5 is a cross-sectional view of an edge-emitting light emitting diode according to another embodiment, FIG. 6 is a partially cutaway perspective view, and FIG. 7 is a diagram showing characteristics. 3...Active layer, optical waveguide layer 10...Light absorption layer agent Patent attorney Nori Chika Ken Yudo Takehana Kikuo Spectrum Mineba Juban

Claims (2)

[Claims] (1) In an edge-emitting light emitting diode in which the active layer that generates light forms a striped optical waveguide and the spontaneously emitted light is extracted from the end face, an energy bandgap near the end face of the optical waveguide is larger than that of the active layer. An edge-emitting light emitting diode characterized by having a non-excited absorption region made of a small compound semiconductor. (2) An edge-emitting light emitting diode that extracts spontaneously emitted light from the end face of a striped active layer that generates light, characterized in that an unexcited absorption region having a scattering surface is provided near the end face. light emitting diode.