Browse Prior Art Database

Type II Superlattice Infrared Photodetector

IP.com Disclosure Number: IPCOM000035968D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 36K

Publishing Venue

IBM

Related People

Chang, LL: AUTHOR [+4]

Abstract

A technique is described whereby a long wavelength photodetector is based on gap tunability, so as to provide a Type II superlattice infrared photodetector with the ability to tailor the effective semiconductor bandgap.

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Type II Superlattice Infrared Photodetector

A technique is described whereby a long wavelength photodetector is based on gap tunability, so as to provide a Type II superlattice infrared photodetector with the ability to tailor the effective semiconductor bandgap.

In prior art, problems have been encountered in the realization of sensitive and reliable infrared photodetectors and imagers. Prime candidates have been various mixtures of II/IV/VI semiconductors, because their attractive bandgap can be tailored by composition. Also, different materials, or alloys, have to be used for each wavelength range of interest. The concept described herein explores a new class of long wavelength detectors. The desired range of bandgap is readily achieved, not by compositional changes, but by the adjustment of the period of a Type II superlattice, which is made with a given set of materials.

The best known and most suitable material is the InAs-GaSb superlattice, with the possibility of alloying either of the binary compounds with GaAs. By varying the period in such a superlattice, it is possible to vary from a wide-gap semiconducting state to a negative gap semimetallic state. Fig. 1 illustrates a pure InAs-GaSb superlattice, where the ground states of electrons and holes are indicated. Their energy difference defines the superlattice energy gap (Egs), which governs the threshold energy of absorption.

(Image Omitted)

It is evident that the wavelength, which is capable of exciting an electron hole pair, covers a wide range. As a result, the infrared detector is simply a Type II superlattice suitably imbedded in a p-n, or a p-i-n junction configuration, so that it can sustain applied voltages. The field created in th...