Patent
1983-09-01
1986-08-26
Sikes, William L.
H01L 3300
Patent
active
046085815
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to semiconductor optoelectronic engineering, more specifically to a structure of semiconductive light-emitters based on gallium nitride and to a process for producing same.
BACKGROUND OF THE INVENTION
Semiconductive light emitters based on gallium nitride and processes for making same have been known for a relatively long time; however, no instrument has been developed hitherto which would possess a stable efficiency of a controlled light emission within a broad range of spectrum (from UV to IR inclusive).
Known in the art is a semiconductive light emitter based on gallium nitride (cf. H. P. Maruska, D. A. Stevenson, Solid State Electronics, vol. 17, No. 11, 1974, pp. 1171-1179), comprising a substrate from a single-crystalline material transparent within the visible range of spectrum with applied thereonto layer of gallium nitride of the n-type of conductivity and an overlaying layer of gallium nitride alloyed with acceptor dopes. The instrument has two metallic electrodes. The metallic electrode on which a negative-polarity voltage is applied is formed on the layer of gallium nitride alloyed with acceptor dopes, while the metallic electrode onto which a positive-polarity voltage is applied is formed on the layer of gallium nitride of the n-type conductivity (in the end-face portion of the layer).
The process for the manufacture of this instrument comprises epitaxial growing, on a substrate of a single-crystalline material transparent within the visible range of spectrum, a layer of gallium nitride of the n-type conductivity, epitaxial growing, on this layer, a layer of gallium nitride alloyed with acceptor dopes; formation, on the endface portion of the first layer of a metallic electrode onto which a positive-polarity voltage is applied and, on the second layer, of a metallic electrode onto which a negativepolarity voltage is applied.
In the above-described light-emitting device the grown layers of gallium nitride comprise aggregated microscopic domains forming an integrated single-crystalline facet structure. The surface of the grown layers comprises alternating projections and recesses.
The structural imperfections and morphological characteristics of the surface of the layer of gallium nitride alloyed by acceptor dopes (alternation of projections and recesses) result in a non-uniform distribution of acceptor dopes in the layer, as well as in a non-uniform distribution of the potential over the layer surface. The acceptor dopes are thus accumulated in projections and recesses of the layers in voids between the grains.
In operation of the device (upon application of an external voltage) the above-mentioned factors cause, in the layer of gallium nitride alloyed by acceptor dopes, the formation of current leakage channels (i.e. low-ohmic regions) or irrevocable breakdown of the layers and, hence, in disappearance of the light emission.
To a certain extent the above-mentioned disadvantages have been overcome in a semiconductive light emitter based on gallium nitride (cf. French Pat. No. 2,363,900 published May 5, 1978). This device comprises a substrate from a single crystalline material transparent in the visible range of the spectrum. A layer of gallium nitride of the n-type of conductivity is applied onto the substrate. A layer of gallium nitride alloyed with acceptor dopes and consisting of two sub-layers is deposited onto the former layer. The first sub-layer is only slightly alloyed with acceptor dopes and deposited directly on the layer of gallium nitride of the n-type of conductivity, while the second active sub-layer is strongly alloyed with acceptor dopes and deposited onto the first sub-layer.
The device also has two metallic electrodes. A metallic electrode to which a negative-polarity voltage is applied is formed on an active sub-layer of the layer of gallium nitride alloyed with acceptor dopes. A metallic electrode to which a positive-polarity voltage is applied is formed on the layer of gallium nitride of the n-type of conductivity.
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REFERENCES:
patent: 4094704 (1978-06-01), Milnes
patent: 4268842 (1981-05-01), Jacob et al.
patent: 4396929 (1983-08-01), Ohki et al.
Akopova Svetlana Z.
Bagratishvili Givi D.
Bogdanovich Viktor B.
Charmakadze Revaz A.
Chikovani Rafael I.
Sikes William L.
Wise Robert E.
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