Performance optimization of long-wave infrared detectors based on InAs/GaSb strained layer superlattices

Relationship between V/III beam equivalent pressure (BEP) flux ratios during the molecular beam epitaxial (MBE) growth of long-wave infrared InAs/GaSb strained layer superlattice (SLS) material, crystalline quality of asgrown material, and devices' signal (responsivity) and noise (dark current) characteristics was investigated. It was found that the V/III ratio is a critical factor affecting the dark current, cut off wavelength and the responsivity of the device. Modest change of As/In BEP flux ratio (from 5.5 to 7) resulted in red-shift of cut-off wavelength by 0.6 μm. Temperature-dependent dark current measurements revealed more than two orders of magnitude difference in dark current densities of detectors grown with different As/In BEP flux ratios. The highest responsivity and QE values, equal to 0.75 A/W and 10% (74K, 9 μm, -0.4V), were demonstrated by the device with highest dark current density and notoptimal structural properties. The observed dependences of devices' signal (responsivity) and noise (dark current) characteristics in conjunction with the structural properties and the growth conditions of SLS material suggest that the good structural properties of grown detector material as well as low noise would not necessary result in improved device performance.