Intraband Processes and New Device Concepts in SemiconductorHomo and Hetero Junctions

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9412248 Perera Research on novel semiconductor device concepts and intraband processes leading to potential applications primarily in high-performance infrared imaging and emitter systems will be performed in which the unique dimensional and compositional control capability offered by recently emerging MBE growth technology will be revised to evolve special types of novel junction and multi-quantum well (MQW) formats. In one such format, developed under a previous NSF program, the interfacial work function in p-i-n homojunctions is controlled at low values (corresponding to optical energies in the VLWIR to FIR range) by heavy doping of the implanted or MBE-grown photo-emitter region. Analytical and experimental approaches aimed at understanding the influence of critical doping and dimensional parameters, and of bias conditions, on detector and array performance be employed to suggest MBE-grown multi-junction structures with the potential for higher performance at more elevated cryogenic temperatures. The main significance of this work is in establishing a technology base for the evolution of large area, uniform detector arrays with a multi-special capability for greatly improved NE T responsivity. Recent successes with VLWIR MQW (A1, Ga, As) detectors will be exploited by extending the cutoff for both photoconductive and photovoltaic (miniband) structures to wavelengths beyond 16 um, and examining transient operation modes as a means of improving response and detectivity. Working in conjunction with MBE experts at Cornell, NRC, UCLA and JPL the feasibility of improved quality of (A1,Ga)As barrier growth, as a means of lowering dark current at longer wavelengths will also be studied. As is the case for Si homojunctions, the inherent uniformity, and their low power requirements, should enable them to out perform HgCdTe detector arrays at longer wavelengths. Encouraging results for MQW IR emitter structures will provide an excellent basis for further modeling efforts and experimental d evices incorporating three-level and triple-barrier features as a means to improve efficiency of population inversion. Other material systems (e.g. InGaAs/InA1As) will also be examined for the potential of high IR emission in the MWIR range. The MQW emitter technology should lead to stable, integratable, large area IR sources at wavelengths extending from MWIR to FIR, for applications currently being addressed by small-area chemically unstable HgCdTe and PbSnTe laser diodes. ***