MULTI-HETEROJUNCTION LARGE-AREA HGCDTE LONG-WAVELENGTH INFRARED PHOTOVOLTAIC DETECTOR FOR OPERATION AT NEAR ROOM TEMPERATURES

This paper describes a new multi-heterojunction (n) under bar(+)p (p) under bar photovoltaic infrared photodetector. The device has been dev eloped specifically for operation at temperatures of 200-300K in the l ong wavelength (8-14 mu m) range of the infrared spectrum. The new str ucture solves the perennial problems of poor quantum efficiency and lo w dynamic resistance found in conventional long wavelength infrared ph otovoltaic detectors when operated near room temperature. Computer sim ulations show that devices with properly optimized multiple heterojunc tions are capable of achieving the performance limits imposed by the s tatistical nature of thermal generation-recombination processes. In or der to demonstrate the technology, multiple heterojunction devices hav e been fabricated on epilayers grown by isothermal vapor phase epitaxy of HgCdTe and in situ As p-type doping. The detector structures were formed using a combination of conventional dry etching, angled ion mil ling, and angled thermal evaporation for contact metal deposition. The se multi-junction (n) under bar(+)p (p) under bar HgCdTe heterostructu re devices exhibit performances which make them useful for many applic ations. D of optically immersed multiple heterostructure photovoltaic detectors exceeding 10(8)cmHz(1/2)/W were measured at lambda, = 10.6 mu m and T = 300K.