JPS6081888A - Surface light emitting laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce a threshold current by minimizing the loss range by composing a Fabry-Perot reflecting mirror of a cap layer and a reflecting film layer. CONSTITUTION:A reflecting film layer 2 in which N type (or P type)-AlxGa1-xAs layers 21 and N type (or P type)-AlyGa1-yAs layer 22 are alternately laminated in multilayers in provided in the first clad layer 3. The thickness of the layers 21, 22 for forming the layer 2 are set to lambda/4n (lambda represents the central emitting light wavelength, and n represents its refractive index). The compositions of aluminums are different from each other, the layer in which the thickness is set to lambda/4n is thus formed to laminate many layers, and then the wavelength of the prescribed range with the central emitting light wavelength is selectively reflected. Accordingly, in a surface light emitting laser having such a reflecting film layer 2, a Fabry-Perot reflecting mirror is composed of the layers 6 and the layers 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an n (or p)-GaAs substrate.
or p) -AlxGa, -xAs layer (referred to as first cladding layer) and AlyGa1-yAs layer (referred to as active layer)
, p (or n) -A 1zGal-zAs layer (referred to as second cladding layer), p" (or n") -GaA
The present invention relates to a surface-emitting laser formed with an s-layer (referred to as a cap layer) and a method for manufacturing the same.

Conventionally, semiconductor lasers have a Fabry-Perot reflector consisting of a pair of parallel smooth reflecting surfaces with both ends of the excitation layer, in other words, the active layer, in which the charges are in an inverted population state to create an optical cavity. was used.

However, manufacturing such a deep surface requires extremely high manufacturing precision, which has been a factor that significantly reduces mass productivity in manufacturing semiconductor lasers. Recently, surface emitting lasers have also been prototyped, but a method of shortening the cavity length by etching has not been used.

By the way, in the active 3 layer, it is sufficient to confine only the carriers and create a population inversion, but in the above method, the threshold current is large because the cavity length is required to be wide and the optical loss region occupies most of the cavity. As a result, only pulse operation at 77K has been confirmed.

An object of the present invention is to provide a laser structure in which the cavity length can be shortened to the emission wavelength and a method for manufacturing the same, and to obtain a surface emitting laser that oscillates at a temperature closer to room temperature.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 is a structural sectional view of this embodiment. 1st
In the figure, the reference numeral 1 indicates an n (or 1)-GaAs substrate (hereinafter simply referred to as the substrate). 2 is n (or p) -A 1xGat-xA in the first cladding layer 3 described later.
s layer 21 and n (or p) -A 1yGa1-yA
s layer 22 (Il+Q+X+y+2 < 1, p
<2% D <4% ×≠y1X≧p, y≧p)
This is a reflective film layer formed by laminating multiple layers alternately. 3 is n
(or p)-AIzGa, -zAs layer (referred to as first cladding layer). 4 is an A1pGa1-pAs-4= layer (referred to as an active layer, where p<z,), and 5 is a p (or n)-AlqGa, qAs layer (referred to as a second cladding layer, where p<q, p+Q<1) ), 6 is a p'' (or n'')-GaAs layer (cap layer). The cap layer 6 is partially etched away, and the middle part 51 of the second cladding layer 5 facing the etched part 61 is removed.
In the non-etched portion 62 of the cap layer 6, n+ (or p''
)-GaAs diffusion layer 7 is formed, and the diffusion layer 7 forms a current passage limiting layer. 8.9 is a metal layer serving as a contact.

Here, the thickness of each of the layers 21 and 22 constituting the reflective film layer 2 is λ/4n (where λ is the center emission wavelength,
n is a refractive index). When a large number of layers A) having mutually different compositions and a film thickness set to λ/4n are laminated in this way, wavelengths in a certain range around the central emission wavelength λ are selectively reflected. Therefore, in a surface emitting laser having such a reflective film layer 2, the cap layer 6 and the reflective film layer 2 constitute a 7-application-Perot reflector. Figure 2 shows the reflectance on the vertical axis and the wavelength on the horizontal axis, and shows the AlxGa, -xAs layers and AlyGa1-yA
The composition in the s layer is x = 0.35 (refractive index n1 = 3°6
), film thickness 570 angstroms, and y=0°7(
FIG. 4 is a diagram showing the reflectance for outside wavelengths when 49 layers are laminated, each having a refractive index (n2=3.3) and a film thickness of 620 angstroms. As is clear from Figure 2, the wavelength λ is 820.
When the thickness is angstrom, the reflectance is about 94%.

Further, the direction of the current is limited by the diffusion layer 7, and the current direction is limited by the diffusion layer 7.
In the active layer 4, the flow is as shown by the broken line 10 in the figure.
A population inversion state is obtained, and this can be achieved by laser oscillation. 11 is a light emitting surface.

As described above, according to the present invention, n (or p)-GaAs
Second, an n (or p)-AlzGa, -zAs layer (referred to as a first cladding layer) and an Al p Ga I
−p A s m (referred to as active layer) and p (or n
)-AlqGal-qAsM (referred to as second cladding layer)
In the surface emitting laser, in which an n(or p)-AlxGa, -xAs layer and an n(or p)-AlxGa, -xAs layer are formed in the first cladding layer. p) -AlyGa1-y
As layer (11.q+X+V+2 < 1, +
1 <zs p <q, X≠y, x≧p, y≧p
), and the cap layer is locally etched and removed, and the cap layer is removed up to the middle part of the second cladding layer facing the second etching removal part and the non-etched part of the cap layer. In the etching removal part, n + (or p")-GaAs is removed up to the middle part of the cap layer.
A diffusion layer is formed, and a current passage limiting layer is formed by the diffusion layer, a hole is formed in the non-etched portion of the cap layer, and the cap layer and the reflective film layer form a Fabry-Perot reflector. In order to create an optical resonator by weakening both ends of the active layer,
It is no longer necessary to manufacture conventional Fabry-Perot reflectors that require extremely high manufacturing precision, and it is now possible to extremely easily manufacture this Fabry-Perot reflector with the minimum required length, that is, the minimum loss area. This makes it possible to significantly reduce the threshold current of the surface emitting diode.

7-

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the structure of an embodiment of the present invention, and FIG. 2 is a diagram showing the anti-AJ ratio with respect to wavelength of the reflective film according to the embodiment. 1 is an n (or p)-Ga As substrate, 2 is a reflective film layer, and 3 is an n (or p)-A 1zGa1-zA
s layer (first cladding layer), 4 is Al p Ga,
-p A s layer (active layer), 5 is p (or n) -A
lqGa+-qAs layer (second cladding layer), 6 is a p-type or n'')-GaAs layer (cap layer), 7 is a diffusion layer,
8 and 9 are metal layer applicants ROHM Co., Ltd. agent Patent attorney Kazuhide Okada 8- (0('J () () period)

Claims (2)

[Claims] (1) n (or p)-GaAs substrate" Second, an n (or p) -AlzGal-zAs layer (referred to as the first cladding layer), an AlpGal-pAs layer (referred to as the active layer), and a p (or n) In a surface emitting laser in which a -AIqGal-qAs layer (referred to as a second cladding layer) and a p+ (or n'')-GaAs layer (referred to as a cap layer) are formed, an n (or p )-Al
xGa, -xAs layer and n (or p) -A IyG
al-yAs layer (however, 11+Q+X+V+2<1,
A reflective film layer is formed by alternately laminating multiple layers of p<z, p<q, x≠Vs A diffusion layer of n + (or p + )=GaAs is formed up to the middle part of the second cladding layer facing the cladding layer and up to the middle part of the cap layer in the non-etched part of the cap layer. A current passage limiting layer is formed, a contact is formed in the non-etched portion of the cap layer, and a contact layer is formed between the cap layer and the reflective film layer.
A surface-emitting laser composed of an Appli-Perot reflector. (2) On an n (or p) -GaAs substrate, an n (or p) -AlzGa, -zAs layer (referred to as a first cladding layer), an AlpGa, -pAs layer (referred to as an active layer), and a p (or n)-AlqGal-qAs layer (referred to as second cladding layer) and p'' (or n'')-GaAs layer (
In a method of manufacturing a surface emitting laser by forming a first cladding layer (referred to as a cap layer),
-A IxGal-xAs layer and n (or p)-A
lyGa, yAs layer (however, p+q+x, y, z<
i, p<z, p<q, x≠5'% Current passage is restricted by diffusing n + (or p + )-GaAs up to the middle part of the second cladding layer facing this etched removed part and in the non-etched part of the cap layer to the middle part of the cap layer. A method for manufacturing an upward surface emitting laser, comprising: forming a layer, forming a contact in a non-etched portion of the cap layer, and forming a 77 Bri-Perot reflector with the cap layer and the reflective film layer.