JPS6083389A - Surface luminescent laser oscillator - Google Patents

Abstract

PURPOSE:To reduce the oscillation threshold-value current density of the titled oscillator by a method wherein two layers or multilayered active layers are simultaneously activated utilizing tunnel current in reversely biased p<+>-n<+> junctions. CONSTITUTION:An n type GaInAsP layer 12 is grown on an n type InP substrate 11, and moreover, double-hetero structures consisting of n type InP clad layers 13, GaInAsP active layers 14 and p type InP clad layers 15 are respectively grown in a multilayer structure through high-impurity concentration p<+>-n<+> junctions of p<+> type InP layers 16 and n<+> type InP layers 17. Voltage is impressed in the forward direction extending over the direction and when tunnel current begins to flow between the p<+>-n<+> junctions 16 and 17 doped in a high-impurity concentration in a reversely biased condition, current begins to flow on the whole laser, carriers are injected in the layers 14 and an inverted population is formed. Resonance generates between optical resonance path 23 and laser beams 24 are outputted from the substrate 11. As current of the same current density as the layers 14 runs on the layers 14, the active regions can be made longer, thereby enabling to reduce the oscillation threshold-value current density.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a surface-emitting laser oscillation device, and in particular to a surface-emitting laser that has a structure in which a plurality of active layers are stacked to reduce the threshold current density of one oscillation. It relates to an oscillation device.

[Technology background]

FIG. 1 shows an example of a conventional surface emitting laser.

In the figure, 1 is an external InP substrate, 2 is a Ga4. A, P active layer, 3 P-type InP cladding layer, 4ζ reflective surface.

5 is an electrode, 6 is a mirror electrode, 7 is a current, 8 is an active region, 9
represents an optical resonance path, and lO represents a laser beam.

The illustrated device allows GcLInAsP
An active region 8 is generated in the active layer 2 to form a Fabry-Bello resonator between the reflective surface 4 and the mirror electrode 6 . As a result, optical resonance occurs along the optical resonance path 9, and laser light 10 is emitted.

As exemplified above, conventional surface emitting lasers.

Since it has only one active layer and the gain region is only as long as the thickness of the active layer, the single oscillation threshold current density is high (for example, approximately 800.A; 77K), and room temperature operation is not possible due to heat generation. The problem was that it was difficult.

In order to reduce the oscillation threshold current density, it is necessary to increase the gain region by forming a reflector with a high reflectance or by increasing the thickness of the active layer. In addition.

If the active layer is simply formed into multiple layers and activated by leakage current from the hetero barrier, the result will be the same as in the case of a single active layer that is 9 equivalently thick.

By the way, the former method of forming a reflecting mirror with a high reflectance has the problem that the laser light output becomes significantly small, and the latter method of forming a thick active layer also has the problem.

The thickness is limited to be less than the carrier diffusion length.1.
! 'Ta. Especially for mouth compounds such as GaInAsP,
In the case of liquid phase growth, there is a problem in that it is difficult to grow a thick film with a uniform composition.

[Object and main points of the invention]

The purpose of this invention is to solve the above-mentioned problems.

The aim is to enable surface-emitting lasers to operate at lower oscillation threshold current densities than conventional ones, and to do so by exploiting the tunneling current in the reverse-biased P-n junction. The above objective is achieved by activating both at the same time.

[Embodiments of the invention]

Figure 2 is a cross-sectional view of one embodiment of a surface emitting laser according to the present invention.

P layer, 14 is GaInAaP active layer, 15 is P type 1nP
15 is a solid layer, 16 is a P-InP layer, and 17 is an n-InP layer.
layer, 18 is P”G aI nA s P cab layer, 19
is S, :02 film, 20 is n-side electrode such as As /S n, 21 is P-side electrode such as A tL / Z n or A a /Cr, 22 is Au reflective film, 23 is optical resonance path, 2
4 indicates a laser beam.

The structure shown is an n-type GαI on an n-type IaP substrate II.
%AsP layer 12 is grown, and further an InP cladding layer 13 and a Ga1nAsP active layer 14 are grown. The tuple heterostructure of the P type + InP cladding layer 15 is replaced by a P-In
P layer 16 * n' High impurity concentration P of LnP layer 17
It is grown in multiple layers through +-n+ junctions.

In the illustrated example, three layers are multiplexed. The last P-type ItL
On the P cladding layer 15, a P"G-I nAs P cab layer 18 is grown to reduce the ohmic contact resistance at the electrode. n-type GαI n 4a
The P layer 12 is used in 1. when fabricating a short resonator structure. P and Ga
This layer is necessary because it takes advantage of the difference in etching speed between InAsP and InAsP.

In this example, in order to limit the area where current flows, 5
(A circular hole is made in the Ox film 19.

A P-side electrode 21 such as A − /Z n or A, /C, etc. is attached. An electrode 20 made of As/Sq or the like is attached to the outside, and a high reflectance A film 22 is attached thereon.

Next, the operation of the embodiment shown in FIG. 2 will be explained. first.

Applying a voltage in the forward direction, the P+, n+ 2 mixture 16- doped to a high impurity concentration in a reverse bias state
When a tunnel current begins to flow between 17 and 17, a current begins to flow throughout the laser, carriers are injected into each Ga In As P active layer 14, and one population inversion is formed. Resonance occurs between the optical resonance path 230, and laser light 24 is output from the substrate 11 side.

Since a current with the same current density J flows through each Ga I'nAs P active layer 14, they are all activated uniformly.

Compared to conventional surface-emitting lasers that only have a single active layer, the active region can be made longer. .

Therefore, the threshold current density for one oscillation can be lowered.

Furthermore, the characteristics of the multilayer active layer are 2. For example, a single active layer structure surface emitting laser with a J thickness of d and a multilayer active layer structure surface emitting laser with a multilayer structure of N active layers with a thickness of d/N are compared. In the case of Because it only costs 1/N.

Jth' can also be reduced to 1/N of Jth, making it possible to significantly reduce the threshold current density for one oscillation by employing a multilayer structure.

In addition, this structure is based on GαAgA3 using a GaAa substrate.
It goes without saying that the invention can be applied to semiconductor lasers in exactly the same way.

〔,Effect of the invention〕

As described in detail above, according to the present invention.

Compared to conventional surface emitting lasers, the oscillation threshold current density can be significantly lowered, and a highly reliable surface emitting laser can be realized. Conventional surface emitting laser has.

In addition to excellent features such as monolithic resonator fabrication, single-longitudinal mode operation due to short resonator structure, Sayama radiation angle, and two-dimensional array formation, it also has high value and reliability due to low threshold operation. The device according to this invention is:

It is expected to be widely used in the construction of future optical integrated circuits, and has extremely important significance.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an example of a conventional surface emitting laser. FIG. 2 is a sectional view of an apparatus according to an embodiment of the present invention. In the figure, 11 is an n-type IRP substrate, and 12 is an n-type GαI. AaP layer, 13 is IsP cladding layer, 14 is GaI
nAsP active layer, 15 is P type I n P cladding layer, 1
6 is P+-InP layer, 17 is n+-ISP layer, 18 is P
+GcLInAsP cab layer, 19 is 5iOz film 120
is A1L/Sn electrode, 21 is A-/zn or A u/(
: , - P-side electrode, 22 is an A14 film, 23 is an optical resonance path, and 24 is a laser beam. Patent applicant Hiroshi Haseyo, Patent attorney, New Technology Development Corporation

Claims (1)

[Claims] + + A surface emitting laser oscillation device characterized in that a plurality of active layers are alternately stacked via Pn tunnel connections to form a multilayer active layer structure.