JPS6215871A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser capable of a modulating operation at ultrahigh speed by incorporating an electrostatic induction or ballistic type transistor in a laser diode itself or fabricating such a transistor in close proximity with the laser diode to thereby lower floating impedance related to wiring or the like. CONSTITUTION:A first clad layer 7, active layers 5, 6 and a second clad layer 4 are provided on a semiconductor substrate 8 for laser oscillation, and a fourth semiconductor layer 3 which absorbs laser light is provided on the second clad layer 4. An opening 14 is provided in the fourth semiconductor layer 3, and a predetermined grid layer 9 is disposed within the opening 14 so that the grid layer 9 is connected to the fourth semiconductor layer 3. A fifth semiconductor layer 2 is disposed on the fourth semiconductor layer 3 including the opening 14. A first electrode 12 is provided on the reverse side of the semiconductor substrate 8, a second electrode 10 on the fifth semiconductor layer 2, and a third electrode 11 on the fourth semiconductor layer 3. In addition, a means which constitutes a resonator for laser oscillation is provided. The active layers 5 and 6 have, for example, a superlattice structure, and, for example, an impurity region is provided underneath and in contact with the second electrode 10.

Description

[Detailed description of the invention] ■Field of application of the invention] The present invention relates to a semiconductor laser.

[Background of the invention]

A semiconductor laser and a transistor are fabricated on the same substrate (usually referred to as monolithic)1, so-called ○
E I C (optoelectronic int,
There are already many examples of egrat, edcivcT+it,). Among these, there is an example in which a field effect transistor (FET) is built on a semiconductor laser via a high resistivity layer. For example, Matsueda et al.; Journal of the Japanese Society of Applied Physics (
Japan, J, Appl, Phys, ) Vo
l, 20 (1981) Suppl, 2o-il pp.
, 193-197, etc. The present invention is.

By using electrostatic induction type or pallitic type transistors, much higher speeds than these conventional examples can be achieved.

Note that, apart from 0FIC, there are many documents regarding static induction transistors or pallitic transistors themselves. For example, Nishizawa et al. (J, NiN15h
iza, et al); IE Transaction Electron Device (IE
E E Trans, E 1ectron Dev
ices), ED-22゜pp, 1l85-197
(Au, 1975), or Nikkei Electronics: Commentary; March 16, 1981 issue pp, 10g-1
28° etc.

[Purpose of the invention]

The present invention provides a semiconductor laser capable of ultra-high speed modulation operation. Specifically, it is possible to achieve a modulation rate of IGbit/s or higher.

[Summary of the invention]

By using electrostatic induction type or pallitic type transistors that are monolithically integrated with the laser, we have achieved higher speed operation than conventional ones. In particular, static induction type or pallitic type transistors,
By incorporating it into the laser diode itself or building it close together, we can reduce stray impedance associated with wiring and take advantage of the inherent high-speed performance of these transistors.

Hereinafter, the present invention will be explained in detail according to examples.

[Embodiments of the invention]

First, an example using an n-type QaAs substrate will be described. FIG. 1 shows a cross-sectional structure of a typical example of the present invention.

On the n-type GaAs substrate (8), MOCVD
(M ejal Organic Chemical
Se
An n-type Ga0156A Qo,a5As cladding layer (7) doped with is formed to a thickness of 2 to 5 μm.

Next, undoped GaAs (5) and undoped Ga
o, 7 A Q o, a 5 to l each of As(6)
An active layer is formed of a superlattice of 3 to 10 circles repeated alternately to a thickness of Onm and 2 to 10 nm. Of course, the active layer may be a normal one. Furthermore, p-type or undoped Ga o doped with Zn, 66 A Q o,
The 46 As cladding layer (4) is doped with Se to a thickness of 0.2 to 1 μm, and the carrier concentration is set to I×10”.
An n-type GaAs light absorbing layer 1 to layer (3) having a size of X 1 'X 1019 cm-3 is grown to a thickness of 0.5 to 1.0 μm. Thereafter, a portion of the light absorption/gate layer is removed by etching to form a groove (14) with a width of 1.0 to 10 μm. On top of this, again by MOCVD method, Zn-doped p
type or undoped G ao, 56 A Q
o, 4s A S cladding layer 1.0-4.0 μm (
2) Grow an n-type GaAs charap layer 0.1 to L, 02m (1) doped with Se. Next, the cap layer (1) and the cladding layer (2) are etched away, leaving the parts involved in laser emission, and the light absorption/gate layer (3) is removed.
expose. A metal electrode (11) is formed on this using a lift-off method. That is, using A u G e N i alloy, after vapor deposition, it was heated at 400°C (±10°C) in H2 gas flow.
) to create ohmic contact. The p-side electrode (10) of the laser is a lift-off for depositing Ti, Mo, and Au.

The n-side electrode (12) is made of AuGeNi alloy, C
r, made by vapor deposition of Au. Both surfaces, which will become light-emitting surfaces, are formed by cleaving.

In order to achieve even more effective modulation, it is applied to the grooves when etching the light absorption/gate layer.

By locally curing the photoresist film (by using a precise photomask or holographic light irradiation), fine n-type GaA
s remains in the form of islands. This is the part number of this n-type GaAg.
- A rectangular parallelepiped with sides of 0.01 to 0.2 μm has a cross section of - sides of 0.01 to 0.2 μm. It is a rectangular comb-shaped grid with a diameter of 01 to 0.2 μm. This grid electrically connects the light absorbing layers (
It is effective to form a pattern that can be used in combination with the gate layer in 3) for connection. FIGS. 2(a) and 2(b) are plan views each showing an example of a pattern. The direction of the grid is
It may be parallel to the laser soot stripe, perpendicular to it, or at a certain angle.

Diffusion of Zn, for example, under the laser P-side electrode (10) to reduce the resistance of the current path is advantageous for further speeding up. This diffusion front is shown at 13 in FIG. especially,
When this front is brought close to the gate island or grid (Fig. 1, 9), and the distance is less than 0.5 μm,
Since the traveling distance of electrons during this time is approximately the same as the mean free path °, speeding up occurs due to the paristic effect.

The operation of the device created as described above was confirmed and the following results were obtained.

Laser threshold, 15-50 mA.

Laser wavelength: 0.77-0.85 am.

Ge l~Applied voltage (peak value) 0.5~1. OV.

Modulation frequency 1~5GHz.

Due to current injection, the carrier concentration exceeds the impurity concentration in the active region during laser operation, and the electrostatic field caused by impurities is screened, so this device can be used as an electrostatic induction type or a pallitic type three-terminal device. Operate. In particular, this effect becomes remarkable when the impurity concentration in the cladding layers shown in FIGS. 2 and 4 is kept low.

Based on the above structure, semi-insulating Ga As
First, an n-type conductive layer is grown on the substrate, and on top of that,
A similar structure may be created by forming each of the layers (1) to (7) in FIG. In this way, the present invention provides semi-insulating Ga
It is also applied to ○EIC creation using As substrate.

Furthermore, highly conductive materials such as oscillating metal silicide using InP-InGaAsP system can also be used. In that case, it is best to pay sufficient attention to the consistency of the interface with a compound semiconductor such as GaAs, and apply a technique such as graphoepitaxy or direct writing selective growth using an ion beam.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of the semiconductor laser of the present invention, and FIG. 2 shows a plan view of the gate portion. ■... Cap layer, 2... P-type cladding layer, 3...
・Light absorption/gate layer, 4... P-type cladding layer, 5...
・Superlattice well layer, 6...Superlattice barrier layer, 7・
... n-type cladding layer, 8 ... n-type substrate, 9 ... gate (island or grid), 10 ... P-side electrode, 11
...Gate electrode, 12...N side electrode, 13...P side diffusion front.

Claims (1)

[Claims] 1. A first cladding layer, an active layer, and a second cladding layer for laser oscillation are provided on a semiconductor substrate;
A fourth semiconductor layer that absorbs the laser beam is provided on the cladding layer of the fourth semiconductor layer, an opening is provided in the fourth semiconductor layer, a predetermined grid layer is disposed within the opening, and this grid layer is 4
at least a fifth semiconductor layer is disposed on the fourth semiconductor layer including the opening, a first electrode is on the semiconductor substrate side, and a second electrode is on the fifth semiconductor layer. and a third electrode from the fourth semiconductor layer, and
A semiconductor laser device comprising means for configuring a resonator for laser oscillation. 2. The semiconductor laser device according to claim 1, wherein the active layer has a superlattice structure. 3. The semiconductor laser device according to claim 1 or 2, characterized in that an impurity region is provided under and in contact with the second electrode. 4. The distance between the front of the impurity region in the fifth semiconductor layer provided under and in contact with the second electrode and the grid layer is 0.5 μm or less. 3. The semiconductor laser device according to item 3. 5. The semiconductor laser device according to claim 1, further comprising at least a sixth semiconductor layer provided as a cap layer on the fifth semiconductor layer.