JP3152461B2 - Light emitting element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an m-band light emitting element.

[0002]

2. Description of the Related Art A 1.5 .mu.m-band light-emitting element used for optical communication is obtained by forming a double heterostructure in which an InGaAs layer having a narrow band gap is sandwiched by an InP layer having a wider band gap on an InP substrate. To stabilize the oscillation wavelength of this light emitting element,
DFB and DBR lasers having a structure provided with a diffraction grating are suitable, but this structure requires a step of forming periodic irregularities in a waveguide as a diffraction grating.

On the other hand, in the field of optical fibers, rare-earth-doped optical fibers utilizing the fact that the emission wavelength due to the transition of the rare-earth in-shell level coincides with the minimum loss wavelength range of 1.5 μm of the silica-based optical fiber used for optical communication. Amplifier research is active ("Er-doped fiber optical amplifier" Suzuki et al .: pp.7-
12, JSPS Photoelectric Interconversion 125th Committee, 134th meeting, 1991.9.14).

[0004]

As described above, in the conventional light emitting device, a step of forming a diffraction grating is required to stabilize the oscillation wavelength, which increases the manufacturing cost.

At present, an InGaAsP-based material is used for a light-emitting element that emits light in a wavelength band of 1.5 μm. However, As and P of a group V element contained in this material have a high vapor pressure, so that
A larger amount of source compounds (PH ₃ ,
AsH ₃ ) is required. Above all, PH ₃ has a decomposition efficiency about one order of magnitude lower than that of AsH ₃ , so a larger amount of source compounds is required.

The present invention has been made in order to solve such a problem, and does not require a step of providing a diffraction grating by doping the resonator with Er. It is an object of the present invention to provide an inexpensive light emitting device capable of obtaining stable light emission of 1.5 μm.

[0007]

According to the present invention, there is provided a light emitting device comprising: a mesa portion having an active layer on a substrate not containing phosphorus;
The active layer is formed at an end of the active layer in the optical waveguide direction, and the active layer is formed.
Multiple layers made of materials different from the semiconductor layer to be formed
An optical waveguide is formed, and the mesa portion and the light
For light-emitting elements whose optical resonator is composed of waveguides
Wherein the optical waveguide is doped with a rare earth element.

[0008]

In the light emitting device according to the present invention, when an operating current is applied, the rare earth element doped in the optical resonator is photoexcited, and the light emitted by the level transition of the rare earth element is amplified through stimulated emission. Then, reflection is repeated at the end face of the active region and reciprocated to emit light with a stable wavelength.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing the embodiments. FIG. 1 is a sectional view of a mesa light emitting device according to the present invention. The light-emitting device has a double hetero structure mesa section in which a GaAs buffer layer, an AlGaAs clad layer, an AlGaAs active layer, an AlGaAs clad layer, and a GaAs cap layer are stacked in this order on a GaAs substrate, and an optical waveguide direction end of the AlGaAs active layer. Si
A resonator is constituted by an Er-doped optical waveguide that forms a part of an optical waveguide by laminating O ₂ , TiO ₂ , and SiO ₂ in this order.

Next, a method for manufacturing a light emitting device according to the present invention will be described. The crystal growth method is MBE, and n-Ga
As substrate ((100) plane) substrate temperature 650 ℃, growth rate 1.3μ
Under the condition of m / h, the following layers are grown to form a double hetero structure. (1) Inject n-GaAs buffer layer with injected carrier density of 1 × 10 ¹⁸ cm ^-3
(Si) 0.5 μm (2) n-Al _0.4 Ga _0.6 As cladding layer injected carrier density 2
× 10 ¹⁷ cm ^-3 (Si) 1.0 μm (3) Al _0.12 Ga _0.88 As Active layer undoped 0.05 μm (4) p-Al _0.4 Ga _0.6 As cladding layer injected carrier density 5
1.0 μm at × 10 ¹⁷ cm ^-3 (Be) (5) Inject carrier density of 1 × 10 ¹⁹ cm ^-3 with p-GaAs cap
(Be) 0.5μm

After that, the end of the double hetero structure in the optical waveguide direction of the AlGaAs active layer is n-AlGa 1.8 μm from the surface.
It is removed by chemical etching up to the middle of the As cladding layer. The etching solution at this time is (H ₃ PO ₄ + 2H ₂ O ₂ + 10H ₂
O), the etching time is 200 sec., And the temperature is 30 ° C.

[0012] 0.2μm of SiO ₂ by an electron beam evaporation method on the etched portions, a TiO ₂ 0.1 [mu] m, Si
O ₂ is laminated in a thickness of 0.2 μm. At this time, about 1 × 10 ¹⁸ cm
^-3 doping to form part of semiconductor laser cavity
An Er-doped optical waveguide is formed.

This light emitting device has a mesa structure of 4 μm width, and has a resonator length of 500 μm including an Er-doped optical waveguide (length 200 μm). The end face of the resonator is coated so as to have a reflectivity of at least 80% for 0.8 μm laser light.

FIG. 2 is a graph showing the current vs. light output characteristics of the light emitting device according to the present invention. As is apparent from FIG. It stably increases in proportion to the current.

Further, since 1.5 μm light generated by the transition in the shell of Er is an interlevel transition and has excellent wavelength stability, the light intensity of 1.5 μm is clearly proportional to the operating current at an operating current of 70 mA or more. It increases stably.

On the other hand, the wavelength of light that efficiently excites Er 0.8
0.8 μm, 0.98 μm among μm, 0.98 μm and 1.48 μm
Can be realized by a material containing no phosphorus. In this case, the OEIC for optical communication (opt
o-electronic integrated circuits) can also be realized on a GaAs substrate.

In this embodiment, a part of the laser resonator is used.
Although the case of doping with Er has been described, the entire resonator may be doped with Er.

In this embodiment, the case where the rare earth element to be doped is Er has been described. However, the present invention is not limited to Er, and other rare earth elements may be used.

[0019]

As described above, the light emitting device according to the present invention can emit light with stable wavelength without providing a diffraction grating.
In addition, an element using a phosphorus-free substrate that requires a large amount of a source compound can emit light with stable wavelength, and thus has an excellent effect of low manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a light emitting device according to the present invention.

FIG. 2 is a graph showing current versus light output characteristics of a light emitting device according to the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50 H01S 3/00-3/30

Claims (1)

(57) [Claims] An active layer is provided on a substrate not containing phosphorus.
A mesa portion, located at an end of the active layer in the optical waveguide direction,
A plurality of materials different from the semiconductor layer forming the active layer
And an optical waveguide formed by stacking layers of
An optical resonator is constituted by the portion and the optical waveguide
A light-emitting device, wherein the optical waveguide is doped with a rare earth element.