Metal–insulator semiconductor properties of molecular-beam epitaxy grown HgCdTe heterostructures

Abstract

By using a new device concept, the limitations of high dark and tunnel currents in metal–insulator semiconductor (MIS) infrared detectors with cutoff wavelengths greater than 10 μm may be reduced. The concept is an MIS device fabricated on an N-isotype heterostructure which consists of a thin (approximately 1 μm) wide-band gap HgCdTe layer on top of a thicker (approximately 5 μm) narrow-band gap HgCdTe layer. The wide-band gap layer increases the tunnel breakdown field and reduces the dark currents of the narrow-band gap detector layer. We report here measurements on this type of device structure which has been fabricated from molecular-beam epitaxy (MBE) grown HgCdTe. On one MIS heterostructure with cutoff wavelengths ranging from 9.2 to 11.5 μm a decrease in dark currents by a factor of 2 compared with MIS dark currents in Texas Instrument’s (TI’s) standard solid-state-recrystallized (SSR) HgCdTe is found. In addition the breakdown field for the heterostructure is increased from approximately 0.6 V/μm found in SSR HgCdTe of comparable band gap to 1.4 V/μm. The MIS heterostructure can also be operated as a two-color detector. Along with these results, analysis and interpretation of the data and modeling of the MIS heterostructure design are presented.