| The proximity fuze application for the U.S. Navy currently operates in the 3–5 μm atmospheric transmission window utilizing four PbSe photoconductors. Because the fuze operates in a transmission window, it is vulnerable to enemy countermeasures such as flares. Thus, it is desirable to operate in the 5–8 μm atmospheric absorption spectrum where short-range detection occurs.; The proximity fuze must be inexpensive (less than {dollar}250 per detector), operate at room temperature, have a fast readout (∼20kHz) for rapid target detection, and be robust. The high speed precludes the use of thermal detectors. HgCdTe has non-uniformity over large areas, difficulty in device processing, high cost in growth and device processing, and poor chemical stability due to its ionic bonding. InAsSb is a III-V material system with superior material properties compared to HgCdTe due to its covalent bonding nature.; In this work, InAsSb photodiodes were investigated for use in the proximity fuze application. A systematic investigation took place to determine the suitable devices. The following devices were studied on GaAs substrates: pπn InAsSb homojunctions, p-i-n InAsSb/AlInSb single heterojunctions, and p-i-n AlInSb/InAsSb/AlInSb double heterojunctions. A growth study of the ternary alloys InAsSb, AlInSb, and GaInSb revealed that AlInSb was the best choice for the barrier materials in the heterojunction devices. Furthermore, it was determined that π-doping was ineffective for the active region due to the presence of the material defects. The double heterojunction photodiode showed the highest response at room temperature. This is due to limiting the thermal generation to the active region, confinement of carriers to one direction, and absorption occurring only in the depleted i-region.; Army Research Laboratory has validated the performance of the photodiodes externally. Thus, optically immersed double heterojunction photodiodes meet the minimum requirements specified for the proximity fuze application for photodiodes with an eight-micron cutoff wavelength. The use of these detectors was substantiated through a successful demonstration in a measurement setup mimicking the proximity fuze environment. |
