DEVELOPMENT OF HOMOJUNCTION BARRIER INFRARED DETECTORS

THE PROJECT INVOLVES THE DEVELOPMENT OF A NEW CLASS OF INFRARED DETECTORS THAT ARE CALLED HOMOJUNCTION BARRIER DETECTORS BECAUSE THE PHOTODETECTION PROCESS INVOLVES EXCITATION OVER SUCH BARRIERS. THE DETECTORS ARE PARTICULARLY PROMISING FOR FOCAL-PLANE-ARRAY APPLICATIONS REQUIRING A HIGH DEGREE OF PIXEL-TO-PIXEL UNIFORMITY IN THE LONG AND VERY LONG WAVE IR REGIONS, AND AT EVEN LONGER WAVELENGTHS OF INTEREST IN ASTRONOMY. PRESENT VERSIONS OF THESE DETECTORS POSSESS LOW QUANTUM EFFICIENCY, A FEATURE SHARED BY OTHER INFRARED DETECTORS WITH HIGH UNIFORMITY SUCH AS SCHOTTKY BARRIER DETECTORS, WHICH ARE USEFUL IN THE SHORT AND MEDIUM WAVE IR REGIONS. UNDER PHASE II THE LOW QUANTUM EFFICIENCY OF HOMOJUNCTION BARRIER DETECTORS WOULD BE SUBSTANTIALLY REMEDIED BY THE DEVELOPMENT OF DETECTORS WITH MARY LAYERS, EACH LAYER CONTAINING A THIN HOMOJUNCTION BARRIER. SUCH MULTILAYERED STRUCTURES CAN BE FABRICATED BY MODERN EPITAXIAL GROWTH TECHNIQUES. THE BOOSTING OF QUANTUMEFFICIENCY IN THIS WAY HAS A PROVEN PARALLEL IN THE AREA OF HETEROJUNCTION, MULTIPLE-QUANTUM-WELL INFRARED DETECTORS. LOW NOISE IS EXPECTED, BASED ON OUR MEASUREMENTS OF DARK CURRENTS LESS THAN 10(-16) AMPERES AT BIAS VOLTAGES OF UP TO5 VOLTS ON SIMPLE SILICON HOMOJUNCTION DEVICES. THE LONGESTWAVELENGTH DETECTED TO DATE IS 200 MICRONS, ACHIEVED BY USING A GERMANIUM HOMOJUNCTION DEVICE. THE PROJECT INVOLVES THE DEVELOPMENT OF A NEW CLASS OF INFRARED DETECTORS THAT ARE CALLED HOMOJUNCTION BARRIER DETECTORS BECAUSE THE PHOTODETECTION PROCESS INVOLVES EXCITATION OVER SUCH BARRIERS. THE DETECTORS ARE PARTICULARLY PROMISING FOR FOCAL-PLANE-ARRAY APPLICATIONS REQUIRING A HIGH DEGREE OF PIXEL-TO-PIXEL UNIFORMITY IN THE LONG AND VERY LONG WAVE IR REGIONS, AND AT EVEN LONGER WAVELENGTHS OF INTEREST IN ASTRONOMY. PRESENT VERSIONS OF THESE DETECTORS POSSESS LOW QUANTUM EFFICIENCY, A FEATURE SHARED BY OTHER INFRARED DETECTORS WITH HIGH UNIFORMITY SUCH AS SCHOTTKY BARRIER DETECTORS, WHICH ARE USEFUL IN THE SHORT AND MEDIUM WAVE IR REGIONS. UNDER PHASE II THE LOW QUANTUM EFFICIENCY OF HOMOJUNCTION BARRIER DETECTORS WOULD BE SUBSTANTIALLY REMEDIED BY THE DEVELOPMENT OF DETECTORS WITH MARY LAYERS, EACH LAYER CONTAINING A THIN HOMOJUNCTION BARRIER. SUCH MULTILAYERED STRUCTURES CAN BE FABRICATED BY MODERN EPITAXIAL GROWTH TECHNIQUES. THE BOOSTING OF QUANTUMEFFICIENCY IN THIS WAY HAS A PROVEN PARALLEL IN THE AREA OF HETEROJUNCTION, MULTIPLE-QUANTUM-WELL INFRARED DETECTORS. LOW NOISE IS EXPECTED, BASED ON OUR MEASUREMENTS OF DARK CURRENTS LESS THAN 10(-16) AMPERES AT BIAS VOLTAGES OF UP TO5 VOLTS ON SIMPLE SILICON HOMOJUNCTION DEVICES. THE LONGESTWAVELENGTH DETECTED TO DATE IS 200 MICRONS, ACHIEVED BY USING A GERMANIUM HOMOJUNCTION DEVICE.