Bell Telephone Laboratories

David P Schinke

Adrian R Hartman

Richard G Smith

James C North

Hans Melchior

A silicon photodetector capable of long wavelength response which includes means for aligning an optical fiber for edge illumination. The detector is formed in a silicon body (11 and 12) with major surfaces lying in the (110) plane. A groove (23) is etched in the body adjacent the detector to produce sidewalls (24) and an end wall (25) lying in (111) planes. The sidewalls form a v-shaped groove with a depth precisely determined by the width of the groove so that an optical fiber (26) placed in the groove is vertically aligned with the detector. The end wall is perpendicular to the surface of the body so that light from the fiber is not refracted from the plane of the detector.

Edge illuminated photodetector with optical fiber alignment

Described is a method of fabricating front-illuminated silicon photodiodes having high quantum efficiency, a short response time, (high gain and low excess noise in the case of avalanche diodes), low dark currents and good reliability. In the fabrication of an n.sup.+ -p-.pi.-p.sup.+ APD the method includes the steps of: (1) epitaxially growing a high resistivity .pi.-type silicon layer on a high conductivity p-type silicon substrate; (2) forming an n-type guard ring in the .pi.-layer; (3) forming a p-type channel stop around the guard ring; (4) forming in the .pi.-layer a p-layer by ion implantation and by driving in the implanted ions by heating in a suitable atmosphere; (5) masking the p-layer and introducing phosphorus into the backside to getter defects and/or impurities; (6) ramping the furnace temperature during steps (2) through (5) to reduce crystalline defects; (7) forming a thin n.sup.+ -layer in the p-layer; (8) forming an anti-reflection and passivation coating on the n.sup.+ -layer; and (9) forming electrical contacts to the substrate, the guard ring and the channel stop so that the latter two contacts overlap the surface portions of the corresponding metallurgical junctions. The n.sup.+ -layer is made extremely thin in order to reduce hole injection caused by light incident on that layer, and the ion implantation-drive step (4) and subsequent steps which involve heating are mutually adapted so that the resultant electric field profile in the multiplication region (p-layer) is substantially triangular. A similar process, which omits step (4), is also described for the fabrication of n.sup.+ -.pi.-p.sup.+ photodiodes.

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Berkeley Heights, NJ, United States of America

David P Schinke