Vertical Transport Study of III-V Type-II Superlattices

Type-II strained layer superlattice (T2SL) semiconductors hold great promise for mid- and long-wavelength infrared photodetectors. While T2SL-based materials have advanced significantly in the last three decades, an outstanding challenge to improve the T2SLs is to understand the carrier transport and its limitations, in particular along the superlattice growth layers. In this dissertation, an overview of the current state-of-the-art InAs/GaSb T2SLs is presented. Fundamental semiconductor device equations and transport properties, including miniband conduction and the drift-diffusion parameters, are reviewed, and the fundamental limiting factors in carrier's transport are discussed. Furthermore, the standard method of electron-beam-induced current technique to measuring these parameters is described. The bulk of the manuscript will then explore the characterization of transport properties in an InAs/GaSb nBp photodetector through a variety of techniques. Through electron-beam-induced-current ($EBIC$) measurements, the minority carrier diffusion length along the growth direction has been measured. The $EBIC$ analysis combined with lifetime measurements using time-resolved microwave reflectance method is then used to calculate the minority electron mobility along the growth direction. Quantum efficiency modeling technique is used as an alternative approach to studying transport and quantify the complex relationships between the device performance and the underlying physics involved in it. Photocurrent-voltage measurement is also used to qualitatively investigate the drift characteristics, such as the field dependence of the drift mobility and drift velocity. Finally, the result of a recent study on the electronic band structure of a series of narrow-band superlattices is summarized.