Santa Barbara Research Center

Herbert L Hettich

Ichiro Kasai

Stephen L Lawrence

Samuel F Pellicori

James E Randolph

The light receiving or back-side surface (22) of an indium antimonide (InSb) photodetector device (10) substrate (12) is cleaned to remove all oxides of indium and antimony therefrom. Passivation and/or partially visible light blocking layers (26, 28) are then formed thereon of a material which does not react with InSb to form a structure which would have carrier traps therein and cause flashing. The optical cutoff wavelength and thickness of the partially visible light blocking layer (28) are selected to suppress the avalanche effect in the device (10) at visible wavelengths. This enables the device (10) to operate effectively over a wide wavelength range including the visible and infrared bands. The passivation and/or partially visible light blocking layers (26, 28) may be a thin layer of a semiconductor such as germanium, or silicon dioxide and/or silicon nitride followed by a partially visible light blocking silicon layer.

Visible and infrared indium antimonide (INSB) photodetector with

A four-layer, wideband anti-reflection coating (30) is formed on a light-receiving surface (22) of an indium antimonide (InSb) photodetector (10) to enable detection of light at visible as well as infrared wavelengths. The layers (30a,30b,30c,30d) each have an optical thickness of approximately one-quarter wavelength at a reference wavelength of 1.6 microns. The refractive indices of the layers (30a,30b,30c,30d) are stepped down from the surface (22), having values of approximately 3.2/2.6/1.9/1.45 respectively. The second layer (30b) is preferably formed of silicon suboxide (SiO.sub.0&lt;X&lt;1) by electron-beam deposition of silicon in an oxygen backfill to obtain a refractive index between the indices of silicon and silicon monoxide. A thin passivation layer (26) of germanium or silicon nitride is formed on the surface (22) under the anti-reflection coating (30) to inhibit a flashing effect at infrared wavelengths after exposing to the ultraviolet (UV) and/or visible light.

Wideband anti-reflection coating for indium antimonide photodetector

An article of manufacture includes a substrate carrying at least two coating layers, one layer being of approximately quarter wave optical thickness, the other layer of approximately two quarter wave optical thickness, with the layers alternating between a material such as a dielectric having a first index of refraction and a second material such as a dielectric having a second index of refraction lower than the first index of refraction. These layers form a filtering system which removes narrow bands of light such as laser wavelengths by efficient reflection while permitting the remainder of the light spectrum to pass through the article. The coating layers have optical thicknesses and indices of refraction appropriate to reflect more than 99% of incident light at one or more predetermined wavelengths of light in the range of about 300 to about 1,200 nanometers and to transmit a substantial amount of all other incident light in the range. These articles are made by an electron beam evaporation technique under vacuum and under controlled conditions of temperature, partial pressure of oxygen, and deposition rates.

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Goleta, CA, United States of America

Herbert L Hettich