JPS60101989A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a multiple quantum well laser having a high output and long life by forming a uniform mixed crystal region to a multiple quantum well structure section and forming a cleavage plane constituting a resonator mirror to the mixed crystal region. CONSTITUTION:An n type Ga1-xAs layer 2 is formed on an n type GaAs substrate crystal 1, and a superlattice layer 3 consisting of N+1 GaAs quantum well layers and N AlyGa1-yAs barrier layers, a p type AlxGa1-xAs layer 4 and a p type GaAs layer 5 are shaped on the layer 2 in succession. A nitride film 6 or an oxide film is patterned to form striped windows 7, and Zn is diffused. Consequently, the superlattice layers in Zn diffusion regions 8 are broken, and uniform mixed crystals 9 are obtained. The crystal is cloven in the vicinity 11 of the center along the stripes 7, and resonator mirrors are formed by the cleavage planes 12. An active region is not exposed in the cleavage planes 12 in a semiconductor laser manufactured in this manner and the laser is protected by the uniform mixed crystals shaped by Zn diffusion, thus obtaining a stable high output.

Description

TECHNICAL FIELD The present invention relates to a semiconductor laser having a transparent window cavity mirror and a method of manufacturing the same.

Prior Art In a so-called multiple quantum well laser in which the active layer of the conventional double heterojunction structure (DH structure) is replaced with a superlattice structure,
The threshold value is significantly lower than that of conventional DH lasers;
It has been reported that the characteristics are stable against changes in ambient temperature (W, T, Tzarbl C, Wgi
sbwch RoC, Miller and R, Dir
bgle, Appl, Phyy, Lttt, 65
(1979) 673).

Figure 1 shows the structure and band diagram of a multiple quantum well laser, where 1 is a GαAs substrate, 2 is an At, G
a1-, As confinement layer, 6 is superlattice layer, 4 is Al z
Ga 1-3 As confinement layer, 5 is GaAs layer, 101
); is included in the superlattice structure 6.
An As barrier layer, 102 is a quantum well layer surrounded by the barrier layer, 103 is a conduction band, and 104 is a valence band. The conduction band and valence band of such a structure (=the injected electrons and holes are distributed in two quantum levels formed in the quantum well layer 102, and contribute to recombination light emission; Since the density of states in is extremely high at the band edges, the possibility of low-threshold Lede is theoretically predicted and demonstrated as above.

As described above, multi-quantum well structure lasers are superior to conventional DH lasers in terms of low threshold values, but there is almost no difference between the two in terms of optical output. The reason for this is that the resonator mirror is destroyed due to the high optical power. Furthermore, even in low-power operation, if the operation lasts for a long time, the resonator mirror deteriorates, and this problem significantly reduces the reliability of the laser diode. The resonator structure of a semiconductor laser generally has interfold surfaces, and the active region is exposed on the interfold surfaces. This is one of the causes of destruction of the laser resonator at high output, and also significantly reduces the long-term reliability of the laser. As a method to improve this, a structure in which the active region is buried in the direction of the cavity resonator has been proposed and implemented. However, in this case, two-step epitaxial growth is essential, resulting in problems of low yield and high cost.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a multi-quantum well laser with a long crystal output and a long lifetime, and a manufacturing method that does not require the two-step epitaxial growth, has a high yield, and is low in cost.

Structure and operation of the present invention The structure and operation of the present invention will be explained in more detail in the following embodiments.

It is known that when impurities such as zinc are thermally diffused or ion-implanted into the AIGaAε-GαA5 superlattice, the superlattice is destroyed and changes to a uniform mixed crystal (W, D).

I, ad, ig, etc., Appl, Phys, Lett
, 38 (1981) 776) The present invention focuses on this phenomenon and obtains a multiple quantum well laser composed of a resonator mirror with a transparent window from a wafer fabricated by one-step (series of treatments) epitaxial growth. , details in second
This will be explained using figures. For purposes of explanation, thermal diffusion of zinc will be used to destroy the superlattice.

In FIG. 2 (α), a Le-type AtxGα1-3;
Superlattice layer 6 consisting of Ga1yAs barrier layer (however, 0<y
<r<1, #≧1), a P-type At3:Ga1-2As layer 4, and a P-type GaAs J depression 5 rfjA are formed in this order in the wafer shape immediately after the growth is completed. Next, in FIG. 2A, a nitride film 5tsN+6 or an oxide film 5in2 is formed on the entire surface and patterned to form striped windows 7, and Zn is selectively diffused. This Z
The n-diffusion is carried out in a gas containing Zn vapor at a temperature of 500°C to 700°C. The superlattice layer in the Zn diffusion region 8 is destroyed and AlyGa1A,? It becomes a uniform mixed crystal (part 9). Next, as shown in FIG. 2(C), the crystal is folded along the stripe 7 near its center 11, and the interfold plane 12 (
A resonator mirror is formed from two pieces. 16 shows the vicinity of the resonator mirror, which has become a uniform mixed crystal due to Zn diffusion. In a semiconductor laser manufactured by such a process, the active region is not exposed at the interfold plane 12 forming the cavity mirror, as in the conventional case, and the active region is uniformly At, 'Gα+ − formed by zinc diffusion. y
'As (part 13) protects the laser, making it possible to realize an extremely stable and high-output laser. Also, this mixed crystal layer AlyGa1-y'A, 9
Since the bandgap of the layer can be made larger than the transition energy rod between the lowest levels of the quantum well, absorption losses in this layer can be almost ignored;
A highly efficient laser can be realized. FIG. 2(d) is a diagram showing the semiconductor laser of the present invention after electrode formation, 14,1
5 is a metal electrode, and 10.10' is a lead wire. In the figure, l is the width of the zinc diffusion region, and this width can be made sufficiently small (for example, about several microns). 12,
12 is the interfold surface, which forms a resonator mirror, and the light is uniformly distributed in the zinc diffusion region! E Al y' Ga 1-y
'As (part 13) is output (in a direction parallel to the page).

Here, in the present invention, Al, 'Gα+ -y' As
To explain that the absorption loss in the layer can be made almost negligible, for the sake of simplicity, the GaA, P layer 102 of the superlattice layer is made of 5OA, AlyGa1-y
Assuming that the As layer 101 has a thickness of 5OA and y=0.3, a uniform mixed crystal "'/'"1-y' obtained from these
When As is N=4, y' can be calculated to be about 0.16. Since the bandgap of AlyGa1-y' As (y'-0,13) is larger than the transition energy between the lowest levels of the quantum well, absorption loss in this layer (160 part) can be reduced, and combined with the thinness of this layer, Absorption loss can be almost ignored.

Above, the case in which thermal diffusion of zinc is used has been described in particular (2) of the present invention, but the present invention is not limited to this (= without limitation)
All methods that can break the regularity of the atomic arrangement of the superlattice structure and make it a mixed crystal are applicable, such as the addition of impurities other than zinc (cadmium, magnesium, Si
, an impurity that becomes a donor or acceptor such as Sn, or an impurity that forms a deep level such as Fe, Cγ, or 0) or an impurity ion implantation method can be applied. Furthermore, a proton irradiation method may be applied.

Furthermore, the present invention is not limited to the superlattice structure made of GaAl-AIGaAs, but can be widely applied to other semiconductor materials such as laser diodes made of other semiconductor materials, such as superlattice structures made of Ga5h-AIGaSb. .

As can be seen from the above explanation of the effects of the invention, AlyGa1-yAε-G
Utilizes the fact that by diffusing or ion-implanting impurities such as zinc or impurities into a multi-quantum well structure in which semiconductor materials such as aA3 are alternately stacked, the material transforms into a uniform mixed crystal Aly'Gα1-y'AI, etc. It is now possible to form a resonator mirror with a transparent window with just one epitaxial growth process (a series of processes), and by using this, the optical power can be reduced to 2
improved more than double. Additionally, since no etching or regrowth steps are involved, the surface flatness of the wafer is preserved, thus simplifying the fabrication process and making it easier to configure other optical or electronic devices on the same wafer. It also becomes easier.

[Brief explanation of the drawing]

Figure 1 (to) and direction are explanatory diagrams and band diagrams of the cross-sectional structure of a multi-quantum well laser, respectively, and Figures 2 (a) to (d)
) is a manufacturing process diagram of the semiconductor laser of the present invention. 1-, QaAs substrate, 2... Le type A1. Gα1-x
AI, 3...AlyGa1-yAs-GaAz quantum well structure (superlattice layer), 4, -p-type At engineering Gα1-yoA3
．． 14 and 15...associate genus 1L10 and 10'...
・Lead wire, 12...Inter-fold surface Patent applicant Nippon Telegraph and Telephone Public Corporation agent Patent attorney Gobe Tamamushi (2 others) Figure 1 Figure 2

Claims (1)

[Claims] (1) Consisting of at least a confinement layer, N+1 quantum wells arranged in a superlattice, and N (N22) barrier layers on the substrate crystal, and a superstructure on the side of the laminated structure. A semiconductor radar comprising a uniform mixed crystal region formed by destroying a lattice layer, and characterized in that the mixed crystal region (= is formed with interfold planes constituting a resonator mirror. (2) The substrate crystal is a type GaAz, each confinement layer is an At5cGα1-, As layer, and the superlattice layer is composed of N+1 GaAz quantum wells and N(Q Al yG
a consists of a barrier layer of 1-yAs, where o<y<z<
1. A semiconductor radar according to claim 1, characterized in that: (5) On the substrate crystal (sequential formation of at least two confinement layers, a superlattice layer consisting of N+1 quantum wells and N (N22) barrier layers arranged alternately, and another confinement layer) Then, the surface is coated with a thin film of silicon nitride or silicon oxide, a portion of which is removed in stripes to create many stripe-shaped windows, and then proton irradiation, thermal diffusion, or ion implantation is performed through the windows. The superlattice layer below the window is broken by introducing impurities to form a uniform mixed crystal region, and then the crystal is folded along the stripe near its center to form a layer between the folds. A method of manufacturing a semiconductor laser, characterized in that a resonator mirror is formed by a surface.