Abstract: PtSi/Si Schottky diode infrared detectors are currently being used in large-area focal plane arrays for imaging in the 3-5 micron atmospheric transmission window. Their photoresponse cuts off at about 6 microns, beyond which they cannot detect infrared ratiation. Because of the nature of Schottky diodes, this cut-off wavelength cannot be adjusted during operation, but is relatively fixed, varying only in proportion of the fourth root of an externally applied bias. This disclosure describes a Schottky diode infrared detector with a voltage-tunable cut-off wavelength. The tunability is obtained by modification of the Schottky diode band diagram by insertion of a SiGe layer, with the appropriate parameters, between the silicide and the Si substrate, making the detector a silicide/SiGe/Si Schottky diode detector. The SiGe/Si interface has a valence band offset that can be used to engineer the shape, or depth profile, of the Schottky barrier.

Abstract: Platinum Silicide (PtSi) layers formed on silicon substrates are well known for their ability to image in the infrared portion of the electromagnetic spectrum out to 5.75 micrometers. The detectors are formed on p-type silicon substrates of <100> orientation. This is the preferred crystal structure for silicon when used for fabrication of Very Large Scale Integration (VLSI). The cooling required for these devices is 77.degree. K., which is needed to reduce thermal currents in the diodes to be significantly below the infrared generated signal. Detector array operation at these temperatures does not allow for operation in space for extended missions because a closed cycle mechanical cooler must be used. We have developed a new PtSi detector which must be fabricated on p-type silicon having a <111> crystal orientation. The detectors have been measured for their cutoff wavelength and barrier height is 0.310 eV which translates to a cutoff wavelength of 4.0 micrometers.

Abstract: A Schottky barrier diode formed of iridium-silicon material having a frequency response encompassing the 3.0 to 5.0 micrometer infrared band. The bandwidth, uniformity of response and silicon base material of such diodes renders them ideally suited for use in large scale focal plane arrays associated with infrared cameras.

Abstract: A two dimensional focal plane array of Schottky photodiodes on a silicon substrate for infrared imaging. The array is designed for mating with multiplexing circuitry and has a self-guarding feature wherein adjacent Schottky electrodes act as guard electrodes. This feature allows a substantial increase of the focal plane area coverage ratio.