JPS5885586A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a stable semiconductor laser in high yield in good reproducibility in one epitaxial growing step by forming a recess shape of groove in a semiconductor layer having an energy gap not larger than an active layer on a semiconductor substrate by utilizing a striped groove of narrow width formed to pass through an Zn diffused layer formed on the substrate, thereby limiting the oscillating mode only to the top of the groove. CONSTITUTION:In a double hetero structure semicondutor laser, the second conductive type semiconductor layer 102 is formed on the first conductive type semiconductor substrate 101, the first conductive type semiconductor layer 104 having an energy gap not larger than an active layer is laminated so that the height is the lowest at the groove on a semiconductor wafer formed with a groove 103 passing through the second conductive type semiconductor layer, the first conductive type semiconductor layer 105 having an energy gap larger than the active layer is laminated substantially in uniform height over the entire surface, an active layer 106 is formed, and the second conductive layer semiconductor layer 107 having an energy gap larger than the layer 106 is sequentially formed advantageously in a semiconductor laser.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stabilized 2N heterostructure semiconductor laser with an emitted transverse mode.

As fiber-based communications have come into practical use, stabilizing the transverse mode of the semiconductor laser that is the light source has become an essential requirement. Various laser structures have been proposed and prototyped to stabilize the oscillator mode, and one of them is the one described by Mr. Imai in Electronics Letters G No. 17%, No. 1, pages 17 to 19, published in 1981. There is a 5IViL laser reported by et al. This semiconductor laser is n
- n-1nP buffer layer on InP substrate, InGaAs
After laminating a P active layer, a p-InP cladding layer, and an n-InGaAsP layer with the same emission wavelength as the active layer, the current injection part is etched in a stripe shape up to the p-1nP cladding layer, and a second epitaxial rad layer is formed. This is a structure in which p-InGaAsP electrodes are sequentially laminated. In this semiconductor laser, an InGaAsP active layer and an n-InGaAsP
Since the layers form a coupling waveguide in the direction perpendicular to the heterojunction, the source is concentrated only in the stripe section due to the difference in the propagation constant of light between the stripe section and the other coupling waveguide sections. Therefore, stable transverse fundamental mode oscillation can be achieved.

However, in this example, two epitaxial growth steps are required to fabricate the device, and the active layer, which has been grown once, is kept in a high temperature atmosphere during the second crystallization, which leads to thermal stress. The shadow V was poorly received, leading to a decline in the number of players.

The purpose of the present invention is to overcome one of the drawbacks of the above I-P, and to provide a 21 hetero semi-dedicated laser in which the oscillation transverse mode is debossed, which can be manufactured in just one epitaxial growth process, and whose manufacturing yield is improved. There is a particular thing.

According to the present invention, in a two-hetero sweeping semiconductor laser having an oily j-type sandwiched between two semiconductor heterojunctions, a second type 1-type semiconductor is placed on a first fathom semiconductor substrate. When the layer is formed, the groove portion of the semiconductor wafer is formed with a groove that penetrates through the second inscription-type semicircular body J-.
A first conductive type semiconductor layer with a smaller energy cap than the active layer is laminated so that the energy gap is lower than that of the active layer, and a first conductive type semiconductor layer with a larger energy gap than the active layer is layered over the entire track. A semiconductor laser is characterized in that the layers are stacked to have a substantially uniform height, and an active layer and a second semiconductor layer with a higher energy cap than the active layer are sequentially formed on top of the active layer. is obtained.

The present invention will be fully explained below with reference to the drawings showing the embodiments.

FIG. 1 shows a cross-sectional view of an embodiment of the present invention.

First, 1. Znk, which is a p-type impurity, is diffused to gg of about ljm to form a Zn diffusion layer 102. There is an oil-tight film on the semiconductor substrate.
Striped grooves 103t by J lithography method
It is formed to have a depth of approximately 1.5 μm and a width of 2 μm so as to pass through the Zn diffusion 7*102 in parallel to the roll> direction.

Then, by liquid phase epitaxial growth method, 14
n-In O,66Ga0.34A with 8m wavelength composition
The sO, 74 layer, 26 layer 104 is formed so that the thickness of the flat part becomes 1 μm, and then the n-InP buffer layer 105 is formed by about 1 μm.
μm113ttm z Tsuzumi Max's non-doped In
O,72Ga O,28As O,61P O,39r
Occupancy W11 ('+6 o, 2μtyi, p-InP layer 1
07 to 25 μm% p-In0.85 GaO, 15A
s0.33P0.67'The electrode layer 108 is laminated one by one with a thickness of 1 μm, and crystal growth is performed.
, 66GaO, 34As O, 74Po, 26 layers 104
grows thicker in the groove part than in the flat part, but the total [11']K
The n-InP buffer layer 105 is grown almost flat over the entire surface so as to have a concave shape only on the surface portion, and the n-InP buffer layer 105 is grown almost flat over the entire surface so as to be on the outside of the groove layer 05.

When applying a positive bias to the P side and passing current through this element,
Since the Zn diffusion layer 102 is present in areas other than the striped grooves 103, a pnpn structure is formed, and a current effectively flows only in the groove portions. As the injection current increases, the active layer 10
The light emitting area of 6 tries to expand, but n
-In O, 66GaO, 34AsO, 74Po, 26
Since the layer 104 is located nearby, the leakage to the buffer layer side becomes a loss, and the horizontal mode cannot be established. Therefore, even if the injection current is applied to the gold layer, it is within a range of about 2 to 3 μm above the trench.

Only the transverse fundamental mode will stably exist.

5- Zn diffusion layer 102 provided in advance before crystal growth
By utilizing narrow stripe-like grooves that are formed so as to penetrate through the laser beam, a semiconductor laser with a deformed transverse mode can be obtained with good reproducibility through a single epitaxial growth process.

Manufacturing step W9 has improved significantly. With this semiconductor laser cut to a cavity length of about 250 μm, a device with an oscillation threshold current of 40 mA and a differential Doji efficiency of about 50% at room temperature was obtained with good reproducibility.

Note that in Embodiment 91 of the present invention, the formation wavelength of the active layer was set to 1.3 μm, and the luminescent composition of the n-InGaAsP layer 104 was selected to be 1.4 μm, but the invention is not limited to InGaAsp layers having such a wavelength composition. , n-InG
It is only necessary that the aAsP layer be a semiconductor material with an energy gap not larger than that of the active layer.

A feature of the present invention is that it utilizes striped grooves with a narrow radius that are formed so as to pass through a Zn diffusion layer previously formed on a semiconductor substrate, so that the energy gap is not larger than that of the active layer on this substrate. By making the semiconductor layer concave in the positive part, is it possible to limit the excavation mode to only the upper part of the skin? As a result, a semiconductor laser with a stabilized excavation mode was able to be used with high steps W and a with excellent reproducibility through just one epitaxial wavelength process.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a semiconductor laser according to an embodiment of the invention. In the figure, 101 is an n-InP substrate, 102 is a Zn diffusion layer, 1
03 is striped attack, 104 is n-In0.66
GaO, 34AsO, 74Po, 26 layers, 105 is n-
InP Buff Ding WI. 106 is In0.72 GaO, 28As0161
Po, 39 active layer, 107 p-InP grading layer, 1
08 is p-In0.85GaO, 15AsO, 33Po
, 67 electrodes added, 109 is p-type ohmic, lithium electrode, 110
is an n-type ohmic electrode. =7- Ll

Claims (1)

[Claims] In a two-layer heterostructure semi-integrated laser having an active layer sandwiched between two semiconductor heterojunctions, a second conductivity type semiconductor layer is formed on the first conductivity type semiconductor substrate, and the second conductivity type semiconductor layer is formed on the first conductivity type semiconductor substrate; A first conductivity type semiconductor layer having an energy gap not larger than that of the active layer is laminated on the semiconductor wafer on which a barrier is formed that penetrates the semiconductor layer, and the first conductivity type semiconductor layer having an energy gap not larger than the active layer is laminated so that the height is the lowest at the # part. A first conductivity type semiconductor layer with a larger energy gap than the active layer is stacked over the entire surface to a nearly uniform height, and on top of that is an active layer and a second conductivity type semiconductor layer with a larger energy gap than the active layer.
A semiconductor laser characterized in that conductive semiconductor layers are sequentially formed.