JPH04137687A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To provide optical etching characteristics against outside input and enable complete current constriction by making the thickness of an oscillator identical to the wavelength in the optical oscillator of energy responding to a second quantum level difference in quantum well structure. CONSTITUTION:When electric current is arranged to flow in a forward direction between electrodes 111 and 101, the light of wavelength responding to a quantum level difference of a quantum well layer 107 is emitted where barrier layers 106 and 109 are 125nm thick respectively while an oscillator is 244nm long. This is identical to a value obtained when the wavelength of 810nm is divided by the refraction factor of 3.32 of the barrier layers 106 and 109 based on the level where n=2, and represents one wavelength of oscillation light where the length of the oscillator is n=2. The loss is marked in terms of laser oscillation where the quantum level is n=1. Under a current injected state, the oscillation of 810nm where the level is n=2 preferentially occurs. When the light of 840nm wavelength is input from the outside under this state, the carriers are pumped up to the level of n=1. The level of oscillation is transferred from n=2 to n=1 where the oscillation wavelength jumps from 810nm to 840nm.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a surface emitting semiconductor laser that emits laser light in a direction perpendicular to a substrate, and furthermore, a surface emitting semiconductor laser that has switching characteristics with respect to externally input light. Regarding.

[Conventional technology] Conventionally, surface emitting lasers with a resonator in the vertical direction of the substrate,
It was something like Proceedings of the 50th Annual Conference of the Japan Society of Applied Physics, Volume 3, p, 909 29a-ZG-7. FIG. 6 is a perspective view showing the light emitting section. (60
2) On the n-type GaAs substrate (603>n-type A I Ga
As / AI As multilayer film, (604)
n-type AlGaAs cladding layer, (605) p-type Ga
After growing the As active layer and the (506) p-type AlGaAs cladding layer, they are etched leaving a cylindrical region (
607) p type, (608) n type, (609) I)
type and (610) p type in this order with AlGaAs.

Thereafter, a (611) dielectric multilayer film was deposited on top of the (610) p-type AlGaAs cap layer, and a (601) n-type ohmic electrode and <612) p-type ohmic electrode were formed to form a surface emitting laser.

[Problems to be Solved by the Invention] However, in the conventional technology, the reflectance of the multilayer film that serves as the resonator mirror is high only for a certain wavelength. It does not perform any functional action. Therefore, even if this is made into a two-dimensional array, various calculation operations cannot be performed. Furthermore, a pn junction is provided in the buried layer as a means to prevent current from flowing to portions other than the active layer, but it is difficult to obtain sufficient current confinement and reactive current cannot be completely suppressed. Suppression of reactive current is
This is an important issue in surface-emitting lasers, and for this reason, even in the conventional example described above, it is difficult to drive continuous oscillation at room temperature. In addition, when the buried layer has a multilayer structure as in the conventional example, it is necessary to consider the position of the interface of the columnar growth layer and the p-n interface of the buried layer, making it difficult to control the thickness of the buried layer and reproduce it. It is extremely difficult to manufacture with good performance.

The present invention is intended to solve these problems, and its purpose is to provide a structure that has optical switching characteristics in response to external light input, allows complete current confinement, and is extremely easy to implement. The object of the present invention is to provide a highly efficient surface-emitting semiconductor laser that can be manufactured.

[Means for Solving the Problems] In order to solve the above problems, the semiconductor laser of the present invention includes: (1) a resonator having a resonator in a direction perpendicular to a semiconductor substrate, and a semiconductor multilayer film formed on the semiconductor substrate side; A surface-emitting semiconductor laser that has a reflective mirror and emits light in a vertical direction has an active layer with a Doji well structure, and the thickness of the resonator is the same as the second quantum well of the quantum well structure. It is characterized in that the wavelength of energy corresponding to the level difference is the same as the wavelength in the resonator.

(2) At least one of the semiconductor layers forming the resonator is columnar, and the periphery of the columnar semiconductor layer is buried with a II-Vl group compound semiconductor layer.

(3) The thickness of the semiconductor contact layer on the light emission side is 01 μm
Above 3. It is characterized by being 0 μm or less.

<4) The II-Vl group compound semiconductor layer is ZnSe, Zn
S, ZnSSe, ZnCd5. It is characterized by being one of Cd5Se.

(5) The lattice constant of the I+-VI group compound semiconductor layer is the same as the lattice constant of the columnar semiconductor layer.

(6) The semiconductor substrate and the quantum well layer are made of GaAs.

(7) The semiconductor substrate is made of GaAs, and the Dojiwell layer is made of InGaAs.

(8) The semiconductor substrate is made of InP, and the quantum well layer is made of InGaAsP.

[Example] FIG. 1 is a perspective view showing a cross section of a light emitting part of a semiconductor laser in an example of the present invention.

(102) n-type GaAs group [1, (103> n-type GaAs buffer layer, (104) n-type AI 11.
vG a [1,3A S layer and n-type A 1 a,tG
a il, 9A 15-bear distributed reflection multilayer mirror (105) n-type A 111.7G a that is composed of s layers and has a reflectance of 95% or more for light around a wavelength of 840 nm.
9.3A S layer and n-type A l l! , tG a [1
, QAS layer, and has a resistance of 9 to 810 nm wavelength.
15 pairs of distributed reflection multilayer mirrors (106) with a reflectance of 5% or more, n-type A 111. aG a B,s
A S barrier layer, <107) quantum well active layer with a film thickness of 100Δ, (lo9> p-type A 1114G a 11.
sA s barrier, (110) p-type A l [+,.

It is formed by sequentially stacking G ail and gAs contact layers.

(106) n-type AI 11. aG a 11. aA
Zn of cylindrical shape is etched to the middle of the s barrier layer, and the surrounding area is lattice-matched to GaAS (Loll).
It is embedded in S Ta1Iss e 1I9a. Furthermore, 4 pairs of (112) Si○2/α on the surface
A -3t dielectric multilayer film was formed using Uenoto machining and cutting, leaving a region slightly smaller than the diameter of the light emitting part. (11
It has a structure in which a p-type ohmic electrode (111) is formed on the surface other than the dielectric multilayer film 2), and an n-type ohmic electrode (101) is formed on the substrate side.

When a current is passed in the forward direction between the electrodes <III) and (101), light with a wavelength corresponding to the quantum level difference of the quantum well layer (107) is emitted. At that time, from the quantum level n = 1 (ma 8
Light with a wavelength of 40 nm has a wavelength of 810n from the quantum level n=2.
m light is emitted. Laser oscillation occurs when a resonator is formed between the lower semiconductor multilayer mirror and the upper dielectric multilayer mirror. In this example, the thickness of the barrier layers (106) and (109) is 122 nm each, and the resonator length is 244 nm.
It is nm. This is the oscillation wavelength of 810 from the n=2 level.
It is equal to the value obtained by dividing nm by the refractive index of the barrier layer, which is 3.32. As a result, the resonator length becomes one wavelength of the oscillated light with n=2. In addition, the lower semiconductor multilayer mirror is AI[1
7G a 11.3A S (film thickness 66.9nm) and A
I [1, +ca A layer (104) in which 15 layers of a89As (film thickness 59.7 nm) are stacked alternately and A l
e, vG a 11.3A S (film thickness 64.5nm)
A layer (105) in which 15 pairs of layers of A 1 a, tG a e, eA S (film thickness 57° 5 nm) are laminated alternately.
It consists of The multilayer film (104) has a high reflectance of 95% for a wavelength of 840 nm, and the multilayer film (105) has a reflectance of about 95% for a wavelength of 810 nm.

FIG. 2 is a diagram schematically showing a cross-sectional structure near the active layer in this example. (202) AI 3. vG
a il, 3A s and (201) A 1 s, tG
A part of the lower reflector consisting of a e9A s, and (
A1θ, tGa[1,6A S barrier layer of (203), GaAs quantum well active layer of (204), and (205)
A I l! , aG a e, 6A s barrier layer,
A part of the upper reflector is shown, which is composed of 5i02 of (206) and α-3t of <207). (208) is n
This is a diagram schematically showing a standing wave of light having a wavelength corresponding to a quantum level of =2. Since the resonator length is one wavelength, the antinode of the wave coincides with the position of the active layer. Therefore, the quantum level n;2(
Radhe oscillation from the oscillation wavelength (810 nm) is likely to occur,
Loss is large for laser oscillation from quantum level n=1 (oscillation wavelength 840 nm), and when current is injected, oscillation at 810 nm occurs preferentially. In this state, when light with a wavelength of 840 nm is input from the outside, carriers are pumped to the n=1 level, and the laser oscillation level changes from n=2 to n.
= 1, and the oscillation wavelength jumps from 810 nm to 840 nm.

FIG. 3 is a diagram showing the spectrum of the optical output in this example. (a) shows the case when current is injected, and (b) shows the case when 840 nm light is input from the outside. It can be seen that the oscillation wavelength jumps due to the above-mentioned reason.

Figure 4 shows the injection current Iin and the external optical input P of 840 nm.
optical output P at in (840 nm) and 810 nm. u
FIG. 7 is a timing chart diagram showing the relationship between t(810r+n+).

The relationship between Pin and P out indicates an optical inverter operation, and various logical operation circuits can be implemented using optical input. Therefore, if the surface emitting semiconductor lasers of the present invention are arrayed on a single semiconductor substrate, a parallel optical arithmetic processor can be obtained.

Furthermore, in the surface emitting semiconductor laser of this example, the Z n S s, ess e e, and ea layers used for embedding are IGΩ.
Very effective current confinement is achieved because the resistance of the layer is reduced and no leakage of the current injected into the buried layer occurs. Furthermore, since the buried layer does not need to have a multilayer structure, it can be easily grown and has high batch-to-batch reproducibility.

Furthermore, Zn5af has a sufficiently small refractive index compared to aAs.
A rib waveguide structure using Iss e a, ea layers achieves more effective light confinement.

FIG. 5 is a diagram showing the relationship between the driving current of the surface emitting semiconductor laser according to the embodiment of the present invention and the oscillation light output from the quantum level n=2. Continuous oscillation is achieved at room temperature, with a threshold value of 0.
An extremely low value of 3 mA was obtained. The external differential quantum efficiency is also high, and suppression of reactive current contributes to improved laser characteristics.

Regarding the film thickness of the contact layer of the surface emitting semiconductor laser according to the embodiment of the present invention, the optimum thickness is 0.1 μm to 0.3 μm.
In this range, the element resistance is low and the external differential quantum efficiency is also high.

Furthermore, the semiconductor substrate is made of GaAS, and the quantum well layer is made of InG.
By using aAs, the oscillation wavelength is 970 nm and 940 nm.
nm, and external input light that is transmitted through the substrate can be used.

Furthermore, the semiconductor substrate is made of InP, and the quantum well layer is made of InGa.
By using AsP, the oscillation wavelength becomes a 1°55 μm band, which also allows use of external input light from the substrate side.

[Effects of the Invention] As described above, according to the structure of the semiconductor laser of the present invention,
The following effects can be obtained.

(1) By combining the reflectance peaks of the semiconductor multilayer film serving as the resonator mirror, it is possible to achieve a switch-notching characteristic due to optical input. Since it has an optical inverter function, logical operations are possible. Since it is an element that emits light in a direction perpendicular to the substrate surface, it is easy to form a two-dimensional array, and therefore, with this structure, it is possible to fabricate a parallel optical arithmetic element.

(2) Since a ■-■ group compound semiconductor layer having a resistance of IGΩ or more is used for embedding, leakage of the injection current does not occur, and extremely effective current confinement is achieved.

Furthermore, the m-v group compound semiconductor layer used for the active layer and the II-
It has a large difference in refractive index from the Group VI compound semiconductor layer, making it possible to confine light more effectively than before.

Therefore, continuous oscillation at room temperature, which has been difficult in the past, can be easily achieved, and the oscillation threshold is low and the external differential m-molecular efficiency is high.

(3) Since the buried layer does not need to have a multilayer structure and form a pn junction unlike the case of using a -V group compound semiconductor layer, it can be easily grown and has high batch-to-batch reproducibility.

(4) By matching the lattice constant of I The interdiffusion of the semiconductor layers in the semiconductor layer is suppressed, and a highly reliable surface emitting laser can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a cross section of a light emitting part of a surface emitting semiconductor laser in an embodiment of the present invention. FIG. 2 is a cross-sectional structural diagram of the vicinity of the active layer of a surface emitting semiconductor laser in an embodiment of the present invention. FIG. 3 is a diagram showing the oscillation spectrum of a surface emitting semiconductor laser in an embodiment of the present invention, (a) is a diagram when current is injected, and (b) is a diagram when external light is further input. FIG. 4 is a diagram showing a timing chart of input current, optical input, and optical output of a surface emitting semiconductor laser in an embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the driving current and the oscillation light output of the surface emitting semiconductor laser according to the embodiment of the present invention. FIG. 6 is a perspective view showing a light emitting part of a conventional surface emitting semiconductor laser. 101)...N-type ohmic electrode <102)
-・---n-type GaAs substrate ((03)・n-type GaAs
s buffer layer (104) (105)...Distributed reflection mirror (105) (203)==--n type A l 11. a
Ga [1,6A S, 7th layer (107) (204>----・Ga As ji child well active layer (109) (205)・----・I) type A
1 [1,4G a 11. aA s cladding layer (110>... p-type A l [1, IG a f3.9A s : l
7 tact time (108) = -4: n S 52as e
2.94 layers (111)...P-type ohmic electrode (112)...5i02/α-St dielectric multilayer film (201)'...-A I 11. IG a6.
gA s layer (202)...A l l+,? G
a a, 3A s layer (206)...Si02
Layer (20?)...α-8I layer (208)...Standing wave in resonator (601)
・・・・・・・・・・・・N-type ohmic electrode (602
)・・・・・・・・・・・・N-type GaAs substrate (60
3>・-・・-n-type A I Ga As / A
IAs multilayer film (604)・・・・・・・・・・・・
・N-type AlGaAs cladding layer (605)...
......p-type GaAs active layer (606)...
......p-type AlGaAs layer (60
7)・・・・・・・・・・・・P-type AIGaAs (6
08)・・・・・・・・・・・・N-type AIGaAs(
609)・・・・・・・・・・・・P-type AIGaAs
(610)・・・・・・・・・・・・p-type AlGaA
S carrier, p notification (611)・・・・・・・・・・・・Dielectric multilayer film (612)・・・・・・・・・・・・P-type ohmic electrode or more Applicant: Seiko Epson Kizobe Tsuchi Suzuki, Patent Attorney Co., Ltd. (1 person) 20th Figure 2 Wavelength (a) (nm) Wavelength (nm) (b)

Claims (1)

[Claims] (1) A surface-emitting semiconductor that has a resonator in a direction perpendicular to a semiconductor substrate, has a reflective mirror formed of a semiconductor multilayer film on the semiconductor substrate side, and emits light in the perpendicular direction. The laser has an active layer having a quantum well structure, and the thickness of the resonator is equal to the wavelength in the resonator of light having an energy corresponding to a second quantum level difference of the quantum well structure. A semiconductor laser characterized by being identical. (2) The semiconductor laser according to claim 1, wherein at least one of the semiconductor layers forming the resonator is columnar, and the periphery of the columnar semiconductor layer is embedded with a II-VI group compound semiconductor layer. (3) The semiconductor laser according to claim 2, wherein the semiconductor contact layer on the light emission side has a thickness of 0.1 μm or more and 3.0 μm or less. (4) The II-VI group compound semiconductor layer is ZnSe, ZnS,
3. The semiconductor laser according to claim 2, wherein the semiconductor laser is made of one of ZnSSe, ZnCdS, and CdSSe. (5) The semiconductor laser according to claim 2, wherein the lattice constant of the II-VI group compound semiconductor layer matches the lattice constant of the columnar semiconductor layer. (6) The semiconductor laser according to claim 1, wherein the semiconductor substrate and the quantum well layer are made of GaAs. (7) The semiconductor laser according to claim 1, wherein the semiconductor substrate is GaAs and the quantum well layer is InGaAs. (8) The semiconductor laser according to claim 1, wherein the semiconductor substrate is InP and the quantum well layer is InGaAsP.