JPS58155787A - Manufacture of semiconductor light-emitting element - Google Patents

Abstract

PURPOSE:To manufacture an optical semiconductor laser having excellent characteristics with superior yield by partially heating a high impurity-concentration semiconductor layer, selectively inverting a conduction type of a low-concentration semiconductor layer by a push-in effect and introducing a current constricting mechanism to the lower section of an active layer. CONSTITUTION:An undoped N<-> type InP layer 10, an N type InP layer 11 to which Te is added, the undoped InGaAsP active layer 12, a P type InP layer 14 to which Zn is added, and an N type InGaAsP layer 15 to which Te is added are laminated onto an N type InP substrate 9 in succession. When YAG laser lights 17 are irradiated while using a metallic film 16 as a mask, the lights 17 pass through the layer 15, and are absorbed selectively by the layer 14. Accordingly, an impurity Zn is pushed into a layer 13, the layer 12, the layer 11 and the layer 10 in succession. A conduction type of the layer 10 is inverted into a P<-> type from an N<-> type at that time. The mask 16 is removed through etching, and Zn is diffused selectively so as to reach the layer 14 while using an SiO2 film as a mask. The current constricting mechanism is formed to the lower section of the active layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an injection type semiconductor light emitting device comprising a double heterojunction layer having a structure that limits the spread of current inside the device.

A semiconductor light emitting device using a heterojunction structure has a wavelength of 0.84
m-band (AjlGa) Muhata, wavelength l#m-band InGa
SP/InPLED has been put to practical use, especially as a light source for optical fiber communications, such as in lasers.

In these semiconductor light emitting devices, it is necessary to limit the spread of current in the active layer in order to increase the luminous efficiency for LEDs, decrease the threshold current density for lasers, and control the 1-oscillation transverse mode. . Particularly in semiconductor lasers, it is desirable that the threshold current be as small as possible in order to enable continuous oscillation at high temperatures and to reduce power consumption. For this reason, methods have been proposed in which current is passed only through the active region as much as possible. The most well-known method is to selectively invert the conductivity type of the top layer by impurity diffusion, or to apply an insulating film such as 08 to the surface and form a current injection region using normal photolithography technology. Although this method has the effect of limiting the area of the current injected from the surface, even in this case, the current injected from the surface gradually spreads toward the inside, and in the active layer. will extend over an area several times larger than that for the current injection region on the surface. On the other hand, since the oscillation region is approximately the same as the surface current injection region layer, the proportion of the reactive current component that is not actually used in the total injection current is quite large. Therefore, the threshold current density increases and the differential quantum efficiency of oscillation decreases. In order to eliminate these drawbacks and further limit the current flow in the active layer, it has been proposed to provide a further current limiting mechanism on the substrate side. A conventional method for manufacturing an OS structure for current limiting provided on the substrate side will be explained based on FIG. a11. Taking the case where the conductivity type of the substrate is nil as an example, a PM semiconductor layer 2 is grown on the substrate 1 as shown in FIG. selectively remove it as shown in Figure 1). then the first one on top of that
As shown in figure (c), the s m'li semiconductor layer 3, the active layer 4,
A pH cladding layer Ssn and a capping layer 6 are sequentially grown.

Next, as shown in FIG.
Impurities are selectively diffused up to the m cladding layer 5 to form a p-type region 7, which serves as a current injection region. In this structure, since there is a current confinement layer on the substrate side, the injected current is limited between the upper and lower sides, and the current spread in the active layer is suppressed.

However, in the above method, it is necessary to perform crystal growth twice to form a p-type current confinement layer, and selective etching must be performed to form a current passing region, which complicates the process. There is a drawback. Other methods for forming the octopus current confinement layer 2 in FIG. 1(d) described above include selectively diffusing impurities into the substrate 1 to invert the conductivity type, or selectively implanting pluton. There are methods to create a locally high resistance region, but each method has the disadvantage that the substrate surface is damaged and a large number of dislocation sources are brought into the epitaxial layer stacked on the substrate, which shortens the device's operating life. be. Furthermore, in order to increase the effect of current confinement, it is necessary to match the relative positions of current injection region layer 7 and current confinement layer 2. Specifically, the center line of the current injection region 7 and the current confinement layer 2
It is necessary that the removed portion, that is, the center line of the current passing region 8, coincide with the center line of the current passing region 8. This alignment is performed as alignment between the mask pattern printed on the glass mask and the current passing region 8 provided inside the crystal in the step of manufacturing the diffusion mask using 7 otolithography described above.
In this case, the alignment accuracy is required to be 1 μm or less, which is actually very difficult.

The present invention provides a new and useful method for manufacturing a current confinement layer that eliminates the drawbacks of the conventional method for manufacturing a current confinement layer as described above.

The gist of the present invention is to provide at least the first IIK of one side of the active layer.
By providing a low concentration semiconductor layer of a conductivity type, providing a high impurity concentration semiconductor layer of a second conductivity type on the opposite side, and selectively heating the high impurity concentration semiconductor layer, the high impurity concentration semiconductor layer is heated. Impurities are locally pushed into the lightly doped semiconductor layer to change the conductivity type of the lightly doped semiconductor layer to a second conductivity type, thereby forming a current confinement layer.

The first conductivity type is already on the first semiconductor layer above the active layer.
In a semiconductor crystal in which a second semiconductor layer opposite to the semiconductor layer is provided, a planar stripe structure in which the current passing region above the active layer is narrowed can be realized by selectively forming the second semiconductor layer. Since a current confinement mechanism cannot be provided in the lower part, it is impossible to significantly lower the threshold current density. In particular, in the present invention, a low impurity concentration semiconductor layer of the first conductivity type is provided below the active layer, and a high impurity concentration semiconductor layer of the second conductivity type is provided above the active layer.
The purpose is to locally heat the high impurity concentration semiconductor layer and selectively invert the conductivity type of the low concentration semiconductor layer by a so-called push effect to introduce a current confinement mechanism in the lower part of the active layer.

According to the present invention, crystal growth can be performed only once, and a semiconductor light emitting device having a current confinement layer under an active layer can be manufactured without processing the substrate. There is also the advantage that alignment between the current injection region and the current confinement layer when forming the current injection region from the surface as described above is not necessary. Hereinafter, the present invention will be specifically explained in detail with reference to examples. In this embodiment, a case will be described in which the present invention is applied to a method of manufacturing a semiconductor laser.

FIG. 2 is an explanatory diagram showing the specific manufacturing process of this example.

First, as shown in FIG. 2 (&), undoped or 〒-doped carrier briquettes 2-5 x 10"aw-"0n-111n are deposited on the nmInP substrate 9 by liquid phase or vapor phase growth.
P layer (thickness 2 μm)10. T・added carrier concentration 3×1
017cm+-3 n-type InP layer (thickness 0.1-〇, 5
711!1) 11, undoped InGaAaP active layer (
Thickness Q, 2jams forbidden band width 0.95eV)12. Zn
P-type InP layer (thickness 2 nm) with doped carrier concentration 2 to 3 x l Q"am-' (thickness 2 nm) 13, Zn doped carrier concentration 1
~2X10'- p+ type InGaAsP layer (thickness 174
mm Forbidden band 0.9S@V) 14°T・addition, carrier concentration 3~4X10 ex C1n type I nGaAa
P layers 15 (thickness: 1jms, forbidden band: 19Z4eV) are sequentially laminated.

Next, as shown in Figure 2), the n WIImG Hatakem Hatake P layer 15
A metal film 16 of Au or Aj is provided in stripes on the 0 surface by vacuum evaporation and ordinary photolithography, and YAG laser light (wavelength 1.06 μm) 17 is pulsed using the metal mask 16 as a mask. (1-IQ
joule, 1 msec or less).

At this time, the surface of the InGaAaP layer 15 other than the metal mask 16 is covered with 8i0,18. YA invaded from the surface
The G laser beam 17 is transmitted through the n-type InGaAaP layer 15,
Since it is selectively absorbed in the p+ type T31GaAsP layer 14, the p+ type InGaAsP layer 14 is instantaneously heated. Therefore, the impurity Zn with a large diffusion coefficient is p-type InP.
The impurity Zn in the p-type InP layer 13 penetrates into the active layer 12, the n-type InP cracked layer 11. Furthermore, they are pushed into the n-type InP layer 10 one after another. Since the degree of Zn pushed in at this time is low, the conductivity type of the n-type InP cladding layer 11 does not change even if Zn is pushed in, but the conductivity type of the n-type InP layer 10 is reversed from n-type to p-type. . In this case, since the YAG laser beam 17 does not penetrate under the metal mask 16, the above-mentioned pushing phenomenon does not occur. Therefore, as shown in Figure 2 (c), the conductivity type of the n-type InP layer 10 is selectively converted to the p-type. Next, the metal mask 16 is etched,
8i0. as shown in FIG. 2(d). Using the film 18 as a mask, selective diffusion of Zn is performed so that the tip reaches the p1 type InGaAmPjll 4, thereby providing a current injection region 20. Next, remove sio[I[18 and create plil]. In the semiconductor laser device thus formed, since there is a current confinement mechanism above and below the active layer, current flows only in a limited region, and the threshold current density is greatly reduced.

In the embodiment described above, the stripe width of the metal mask 16 was 10 to 201 m. In this case, the width of the current passing region between the current confinement layers 190 under the active layer is 5 to 15 #m. Further, as is clear from the description of the embodiments described above, there is no need to align the current injection region 20 and the current confinement layer 19 under the active layer 12, so there is an advantage that manufacturing becomes very easy. In the above-mentioned embodiment, the n II InP layer was provided for the purpose of preventing the n-type InP layer lO from being inverted to the p-type during crystal growth, but depending on the growth conditions, the n - type InP layer 1 layer 0
It goes without saying that even when the upper active layer 12 is laminated, a current confinement structure can be produced in the same manner.

Further, in the above embodiment, oscillation efficiency and the like are taken into consideration.

Although the p-type InP layer 13 was sandwiched between the active layer and the p+-type InGaAsP layer 14 of high degree, the p+-type I
An nGaAsP layer 14 may also be formed.

As explained above, according to the present invention, a current confinement layer for suppressing the spread of current flowing in the active layer is provided inside the crystal under the active layer by locally heating the high impurity concentration layer by laser beam irradiation. Not only is it unnecessary to process the substrate, but also the current injection region can be fabricated without the need for alignment with the current confinement layer.

In the above embodiments, a semiconductor laser was used as an example of the semiconductor light emitting element, but it goes without saying that the present invention can be applied to a light emitting diode in exactly the same manner. It can also be applied to heterotetrastructure materials other than the InGaAaP/InP system, such as (AA!Ga)AI double heterostructure, single heterostructure, and homojunction structure.

Thus, according to the manufacturing method of the present invention, this has been difficult in the past. Optical semiconductor devices such as semiconductor lasers having excellent characteristics such as low threshold current and high efficiency can be easily manufactured with high yield, and the effect is great.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing the manufacturing process of a conventional example, and FIG. 2 is a partial sectional view showing the manufacturing process of an embodiment of the present invention. In the figure, l...n-type semiconductor substrate, 2...pH semiconductor layer, 3...n-type cladding layer, 4...active layer%5
... p-type cladding layer, 6... n-type cap layer, 7.
... Impurity selective diffusion layer, 8... Current passing region, 9...
・N-type IIF substrate, 10-n-type InP layer, 11”n
Type 1mP cutted layer, 12-InGaAsP active layer,
13 =-p type InP cladding layer, 14- p+ type In
GaAsP M s 15 ・= n-type InGaAsP
Cap pigeon, 16...metal mask, 17...YAG
Laser light, 18...810. Film, 19... p'' type InP current confinement layer, 20... current injection region, 21...
- P-type electrode 522...n-type electrode, 23... current passing region. ry (0) (1> (C) (d)

Claims (1)

[Claims] forming a layered structure comprising at least a gi conductivity type low-density semiconductor layer on one side of the active layer and at least a second conductivity type high impurity concentration semiconductor layer on the opposite side;
A method for manufacturing a semiconductor light emitting device, comprising the step of selectively inverting the conductivity type of the low conversion semiconductor layer by locally heating the high impurity concentration semiconductor layer.