III-V Semiconductor Unipolar Barrier Infrared Detectors

The II-VI semiconductor HgCdTe (MCT) is the most successful infrared photodetector material to date. MCT grown on nearly lattice-matched CdZnTe (CZT) substrate offers continuous cutoff wavelength (λ
_cutoff
) coverage from the short-wave infrared (SWIR) to the very long wavelength infrared (VLWIR), while providing high quantum efficiency (QE) and low dark current for high-performance applications. In general III-V semiconductors are more robust than their II-VI counterparts due to stronger, less ionic chemical bonding. III-V semiconductor-based infrared focal plane arrays (FPAs) excel in operability, spatial uniformity, temporal stability, scalability, producibility, and affordability. InGaAs FPAs with λ
_cutoff
~1.7 μm perform at near theoretical limit and dominates the SWIR FPA market. Despite a significantly lower operating temperature than MCT, InSb FPAs (Λ
_cutoff
~5.3 μm) dominate the mid-wavelength infrared (MWIR) market in volume due to superior manufacturability and lower cost. The limitation for traditional bulk III-V semiconductor detectors grown on (nearly) lattice-matched substrates is the lack of broad cutoff wavelength adjustability.