Coherent light generators – Particular active media – Semiconductor
Patent
1986-06-27
1989-04-11
Davie, James W.
Coherent light generators
Particular active media
Semiconductor
357 17, 357 61, 372 44, 372 75, H01S 319
Patent
active
048212741
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electro-optical devices for emitting light radiation from a semiconductor medium which is subjected to controlled energy excitation.
2. Description of Related Art
Electro-optical semiconductor devices, for example light-emitting diodes (LEDs), semiconductor lasers, etc., have become widespread over the last few years. This is true, in particular, of lasers suitable for use in optical fiber telecommunications.
One of the problems which arises is developing lasers suitable for emitting in the transparency range of the optical fibers used. Thus, the use of silica based optical fibers requires lasers which emit in the infrared over a range of wavelengths extending from 1.3 .mu.m to 1.7 .mu.m.
The first semiconductor lasers were made with samples of gallium arsenide GaAs. However, the conditions required for obtaining a laser effect were particularly Draconian since the effect could only be obtained at a very low temperature using pulses at a very low repetition rate.
GaAs lasers have since been made to operate continuously and at ambient temperature, but at the price of using complex and heterogeneous structures which are known as "heterojunctions".
In addition to being complex in structure, it should be observed that GaAs lasers suffer from the major drawback of not emitting in the transparency range of optical fibers (1.3 .mu.m to 1.7 .mu.m). Conventional GaAs lasers emit at a wavelength of about 0.9 .mu.m which corresponds to emission at the band edge of the material, i.e. at the transition of the forbidden band situated between the conduction band and the valence band.
Quaternary GaInAsP lasers are also known, and they emit around 1.5 .mu.m, however the semiconductor material must then be associated with a substrate such as an InP substrate.
SUMMARY OF THE INVENTION
The present invention makes it possible to provide a laser which emits about 1.5 .mu.m using a material having a shorter wavelength corresponding to the condution band to valence band transition, typically 0.87 .mu.m for GaAs.
The laser effect can thus be obtained with such a material without being constrained to make use of emission at the edge of the forbidden band.
The invention is based on the surprising discovery that a doped semiconductor medium, as known per se and used heretofore as a substrate, can be used as an electro-optical device under conditions of controlled excitation energy. Such an electro-optical device may be made into a laser or into a light-emitting diode.
The semiconductor medium on which the invention is based is a doped binary, ternary, or quarternary semicondcutor alloy, namely an III-V semiconductor alloy comprising at least one element from column III and at least one element from column V of the Periodic Table, and doped with vanadium, titanium, or niobium.
The column III element is advantageously gallium or indium, or possibly aluminum, and the column V element is advantageously arsenic or phosphorous.
The preferred semiconductor alloys in accordance with the invention are the following binary alloys GaP, GaAs and InP, with special preference going to GaAs, at least in laser applications.
Suitable ternary alloys are Ga.sub.l-x, Al.sub.x As and GaAs.sub.l-x P.sub.x and suitable quarternary alloys are of Ga.sub.l-x, In.sub.x, As.sub.l-y, P.sub.y.
It has been observed that the light emission obtained with an electro-optical device in accordance with the invention is light-emission corresponding to internal emission in vanadium in the form of V.sup.3+, which corresponds to a wavelength lying between 1.5 .mu.m, and 1.8 .mu.m, depending on the material used.
When the dopant is titanium, the emission is internal to the titanium in the form Ti.sup.2+ or Ti.sup.3+. When the dopant is niobium, the emission is internal to niobium in the form Nb.sup.3+.
The transition responsible for this light emission is not fully understood. It appears that the transition is a 1E or 3T2.fwdarw.3A2 transition (for V.sup.3+, Ti.sup.2+, and Nb.sup.3+) o
REFERENCES:
U. Kaufmann et al, "Spectroscopic Study of Vandium in GaP and GaAs", Physical Review B, vol. 25, No. 9, May 1, 1982, pp. 5598-5606.
A. Mircea-Roussel et al, "Optical Absorption and Photoluminescence of Vandium in n-Type GaAs", Solid State Communications, vol. 36, pp. 171-173, 1980, pp. 171-173.
G. Guillot et al, "Decay of 3d Element Internal Photoluminescence Transitions in III-V Semiconductors", Journal of Luminescence, 31 & 32 (1984), pp. 439-441.
Clerjaud Bernard
Deveaud Benoit
Guillot Gerard
Naud Claude
Centre National de la Recherche Scientifique
Davie James W.
Etat Francais Represente par le Ministre des PTT
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