Optical quality in strain-balanced InAs/InAsSb superlattices grown with and without Bi surfactant

Strain-balanced InAs/InAsSb superlattices can be tuned to absorb and emit across the mid- to long-wave infrared, and exhibit appropriate minority carrier lifetimes for high performance infrared photodetectors. The optical quality of this material has been shown to improve with the use of Bi as a surfactant. Specifically, InAs/InAsSb superlattices grown at 425 °C and 430 °C exhibit improved photoluminescence intensity for Bi/In flux ratios up to 1.0%, and optical quality improves further with increasing growth temperature and increasing Bi/In flux ratios up to 5.0%. The identification of optimal growth conditions for InAs/InAsSb superlattices with Bi surfactant, as well as further exploration of the impact of Bi surfactant is an important component to further developing and optimizing this infrared material system. Several strain-balanced InAs/InAsSb superlattices are grown using molecular beam epitaxy at temperatures ranging from 425 °C to 475 °C using Bi/In flux ratios ranging from 0.0% to 10.0%. The structural and optical properties of the samples are evaluated using X-ray diffraction, secondary ion mass spectrometry, and photoluminescence spectroscopy. Analysis of the mass spectrometry data indicates that surfactant Bi incorporates into the InAs/InAsSb material system with a sticking coefficient of 0.3% at 450 °C, yielding dopant-level concentrations for typical Bi/In surfactant flux ratios. Analysis of the integrated photoluminescence intensity indicates that photoluminescence efficiency is greatest with a 1.0% Bi/In flux ratio for growth at 425-430 °C, and a 5.0% Bi/In flux ratio for growth at 450-475 °C. The improvement in photoluminescence efficiency is associated with a longer Shockley-Read-Hall lifetime in the superlattices grown with Bi surfactant.