Electronic Structure and Defect Modeling of III-V(Sb)Superlattices with hybrid DFT

Infrared detectors are widely used in both military and civilian applications and have been researched extensively in the last two decades. Such applications include detection and tracking of hot objects at a long range, passive night vision, finding people in collapsed buildings, astronomy, and bio-medical imaging. The IR portion spans a wavelength range from 1.0 to around 300 μm and is loosely further classified into near-IR (1-5 μm), mid-wave IR (5-12 μm), longwave IR (12 -25 μm), and far IR (25-300 μm). Transitions between vibrational quantum states typically occur in the infrared. Thus, in applications that desire the observation and identification of chemical species using point detection or stand-off detection, such as pollution monitoring, gas leak detection, gas sensing, and spectroscopy, one needs to work in these wavelength bands. The spectrum of black-body radiation has a peak of around 10μm at room temperature. This makes detectors that have a range between 8-12μm very helpful to identify heat radiation from a target at around 300K. Earlier military applications withstood the expense of the less stable and more convenient HgCdTe alloy. The extremely small change of lattice constant with composition makes it possible to grow high quality layers and heterostructure. However, there are multiple problems associated with HsCdTe IR detectors such as large tunneling dark currents caused by the narrow band gap (less than 0.1 eV). InAs/GaSb type-II strained layer superlattices (SLS) have attracted considerable research interest for use as IR photodetectors due to their suppressed Auger recombination relative to bulk mercury-cadmium-telluride (MCT) materials which leads to improved temperature limits of spectral detectivities[18]. Superior performance of InAs/GaSb SLS has been theoretically expected, but is yet to be observed experimentally. It is believed that this is a result of Shockley-Read-Hall (SRH) recombination which causes increased levels of dark current. The eventual goal of my research project for the REU program at CHTM is to apply Sandia Labs’ Socorro code to InAs/GaSb SLS structures and obtain physically accurate results for ideal structures and to then incorporate defects in