Quantitative Study of Compositional Uniformity and Interfacial Strain in InAs/InAs1-xSbx Type-II Superlattices

For infrared photo-detection in mid-wavelength and long-wavelength range, mercury cadmium telluride (MCT) semiconductor alloys remain the most widely used material system despite its major disadvantages of intrinsic Auger recombination and small effective mass. Type-II superlattices (T2SL) have been proposed as possible alternatives to MCT because they may overcome these problems by flexible and more controllable band structure engineering through SL layer thickness/composition and coherent interfacial strain, along with other benefits such as higher mechanical strength and lower cost [1,2]. InAs/Ga1-xInxSb T2SL, the most studied III-V T2SL material system, suffers from short minority carrier lifetime possibly due to Shockley-Reed-Hall recombination, whereas the more recent Ga-free T2SL InAs/InAs1-xSbx has demonstrated significantly improved minority carrier lifetime [3]. This current study uses extensive quantitative characterization of SL layers with nm-scale spatial resolution to explore possible performance-limiting factors: period thickness/composition variation and interfacial strain.