Impact of Be-doping on InAs/InAsSb type-II superlattices for infrared detection

InAs/InAsSb superlattices (SLs) are promising materials for mid- and long-wavelength infrared (MWIR, LWIR) photodetectors due to the recently reported longer carrier lifetime than those of InAs/GaSb SLs at 77 K. However, the lifetime results are for unintentionally-doped $n$-type InAs/InAsSb SLs. Photodetectors with $n$-type absorbing regions rely on hole minority carrier transport to generate the current. This can be a disadvantage in SL photodiodes where the hole mobility in the vertical direction is extremely small at low temperatures, making collection of photo-generated minority carriers at varying depths difficult. Therefore, $p$-type SL absorber materials are preferred. However, if there is a high density of trap states or recombination sites due to the intentional dopants that limit the electron recombination lifetime, a longer hole lifetime that is traded for a higher electron mobility may result in a negative effect on the overall electrical properties, depending upon the magnitude of the lifetime and mobility changes. The carrier lifetimes and material properties of $p$-type InAs/InAsSb SLs have not been investigated yet and represent a crucial next step in developing the material for detectors. A systematic study of the impact of varying Be-dopant density levels on the InAs/InAsSb SL optical and electrical properties is performed using photoluminescence, photoconductive response, and Hall measurements.