JP2574670B2 - Surface emitting laser - Google Patents

Description

The present invention relates to a surface emitting laser using a PN junction and a method for manufacturing the same.

Conventionally, a semiconductor laser uses a Fabry-Perot reflecting mirror comprising a pair of parallel and smooth reflecting surfaces by cutting both ends of an active layer, that is, an active layer in which electric charges are in an inverted distribution state in order to form an optical resonator. I was However, this fabric
Since the light reciprocating between the Perot reflectors is amplified only in one local active layer, the light is absorbed in portions other than the active layer, so that it is general to satisfy the laser oscillation conditions. It was more difficult than a simple laser. For this reason,
There was no semiconductor laser capable of laser oscillation at room temperature.

SUMMARY OF THE INVENTION An object of the present invention is to provide a structure of a surface emitting laser capable of laser oscillation at room temperature and a method of manufacturing the same.

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. In FIG. 1, reference numeral 1 denotes an n (or p) -GaAs substrate;
Is a reflective film layer formed by alternately stacking n (or p) -AlpGa1 _- pAs layers 21 and n (or p) -AlqGa1 _- qAs layers 22; The n (or p) -AlxGa1 _- xAs layer 31, the AlyGa1 _- yAs layer (active layer) 32, and the p (or n) -AlxGa1 _- xAs layer 33 (where y <X, p ≠ q, p> y, q> y)
This is a composite layer that forms a set. The p (or n) and n (or p) AlxGa ₁ -xAs layers that are in contact between the composite layers 3, 3,...
At 31 and 33, tunnel junctions 34 having carrier concentrations of p ⁺ and n ⁺ at least in contact with each other are formed. Reference numeral 4 denotes an n-GaAs layer, which is a current blocking layer. The current blocking layer 4 is locally etched away, and the center of the p (or n) -AlxGa ₁ -xAs layer 33 which is the uppermost synthetic layer facing the etched removed portion 41 and the current blocking layer 4 are removed. The p (or n) -AlxGa1 _- xAs layer and the p (or n)-
A diffusion layer 5 composed of a GaAs layer is formed continuously by diffusion. Further, the current blocking layer 4 may be formed on the n (or p) -GaAs substrate 1. 6 is Ti layer, 7 is
An Au layer, 8 is an AuGe layer, and 9 is a light emitting surface.

The thickness of each of the layers 21 and 22 constituting the reflective film layer 2 is λ / 4n (where λ is the central emission wavelength and n is the refractive index).
Is set to Al compositions are different from each other and the film thickness is λ
When a large number of layers set to / 4n are stacked in this manner, a certain wavelength around the center emission wavelength λ is selectively reflected. Therefore, in the semiconductor light emitting device having such a reflective film layer 2, the emitted light is not absorbed by the substrate 1, the external quantum efficiency is improved, and light can be emitted with extremely high emission intensity. Further, in this example,
A current blocking layer 4 is formed on a portion other than the light emitting surface 9 on the uppermost synthetic layer 3, and a diffusion layer 5 having a small resistance value is continuously formed on the entire surface extending over the light emitting surface 9 and the current blocking layer 4. Is formed. Therefore, the light emitting surface 9 excluding the current blocking layer 4
Since the resistance value of the portion becomes small, current flows intensively only in this portion 9, and the luminous efficiency is increased. Moreover, since the diffusion layer 5 is formed on the entire surface, there is no need for a mask. Further, since the Ti layer is in contact with the diffusion layer 5 over a wide area except for the light emitting surface 9, there is no danger of poor connection or increase in contact resistance. Further, even if the number of the synthetic layers 3 is smaller than that of the conventional one, the reflective film layer 2 is formed.
The semiconductor light emitting device has high luminance due to reflected light emitted by the light emitting device. FIG. 2 shows the composition of the AlxGa1 _- xAs layer as x = 0.35 (refractive index n1 = 3.6), film thickness of 570 Å, and x = 0.7
(Refractive index n2 = 3.3), total thickness of 620 angstrom 49
It is a figure which shows the reflectance with respect to the wavelength when layers are laminated. As is apparent from FIG. 2, the reflectance is about 94% when the wavelength λ is 820 nm. Thus, according to this embodiment, a very efficient surface emitting laser can be obtained.

As described above, according to the present invention, an n (or p) -AlpGa _1- pAs layer and an n (or p) -AlqGa _1- qAs layer are alternately stacked on an n (or p) -GaAs substrate. Is formed on the reflective film layer, and n (or p) -AlxG
a _1- xAs layer, AlyGa _1- yAs layer, p (or n) -AlxGa
_1- xAs layer (however, y <x, p ≠ q, p> y, q> y)
And a predetermined number of composite layers having three layers as one set are formed,
The p (or n) and n (or p) AlxGa ₁ -xAs layers that are in contact with each other between the synthetic layers are formed so that the carrier concentration at least at the contacting portion is such that a homojunction is formed at the joining portion. On the uppermost composite layer or the n
A current blocking layer is formed on at least one of the (or p) -GaAs substrates except for local areas by diffusion, etching, or the like,
Since the diffusion layer is continuously formed on the surface of the current blocking layer and on the local area where the current blocking layer is removed, a plurality of active layers have the same cavity length, and the gain in the cavity is 1 unit. When the gain per layer is G, the power becomes G to the nth power, the threshold current decreases,
Thus, a structure capable of laser oscillation even at room temperature and a method for manufacturing the same can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of the present invention, and FIG. 2 is a diagram showing the reflectance with respect to the wavelength of the reflection film according to the embodiment. 1 is an n (or p) -GaAs substrate, 2 is a reflective film layer, 3 is a synthetic layer, 4 is an n (or p) -GaAs layer, 5 is a diffusion layer, 6
Is Ti layer, 7 is Au layer, 8 is AuGe layer

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-48192 (JP, A) JP-A-50-68288 (JP, A) Proceedings of the 1984 IEICE General Conference (Section 4) No. . 961

Claims (1)

(57) [Claims] An n (or p) -AlpGa ₁ -pAs layer and an n (or p) -AlqGa ₁ -qAs layer on an n (or p) -GaAs substrate.
A reflective film layer is formed by alternately laminating layers, and an n (or p) -AlxGa1 _- xAs layer and an AlyG
a _1- yAs layer and p (or n) -AlxGa _1- xAs layer (however,
y <x, p ≠ q, p> y, q> y), a predetermined number of composite layers each including three layers are formed, and p (or n) and n (or p) in contact with each other between the composite layers. The above AlxGa1 _- xAs layers are formed such that the carrier concentration at least at the contacting portion is a concentration at which a tunnel junction is formed at the joining portion, and is formed on the uppermost synthetic layer or at the n (or p)- Ga
A current blocking layer is formed on at least one of the As substrates except for a local portion by diffusion, etching, or the like, and a diffusion layer is continuously formed on the surface of the current blocking layer and on the local portion where the current blocking layer is removed. A surface emitting laser.