Advanced quantum structures for infrared detectors

Abstract

2025Type-II superlattices (T2SLs) have emerged as promising alternatives to the more established bulk material systems for infrared (IR) photodetection. This is due to predicted fundamental advantages, such as the tunability of the band gap and theoretically reduced Auger recombination rates. However, the superiority of these materials has not been experimentally realized, prompting the need for further investigation. A bottleneck in the development of improved superlattice (SL) structures and devices is the cost in time and resources required to prototype and characterize these materials as well as incomplete knowledge of the material properties and physical phenomena that characterize these structures. Therefore, the field would greatly benefit from simulation methodologies that enable the development of advanced T2SL materials. In this work, the field of IR photodetection is reviewed highlighting the most common T2SLs structures currently being experimentally implemented. A quantum transport model that includes the necessary physical mechanisms to model carrier transport in these structures will be presented. The results of an investigation on the extraction of vertical carrier mobility, a property important for carrier collection, from quantum transport simulations is presented for an example T2SL. It is demonstrated thatcarrier transport in these structures can be highly coherent. In this case, the apparent mo-bility is suppressed due to ballistic resistance, requiring care when predicting the intrinsic mobility of these materials. The best method of mobility extraction is one that considers the dependence of the resistance on device length. This method was applied to predict the quantum efficiency (QE) in curved focal-plane arrays composed of n-type mid-wave InAs/InAsSb and InAs/GaSb structures subjected to the effects of superlattice disorder and external strain imposed by the curving procedure. It is demonstrated that the external strain has a minimal impact on the QE relative to disorder in both structures suggesting the device design could be viable. Additionally, it was found that large magnitudes of positive axisymmetric strain could result in enhanced hole transport. Finally, a comprehensive investigation is presented that probed for optimized n-type long-wave InAsSb/InAsSb SL structures, a material known to result in low QE devices, for various substrate lattice constants. Several structures were found demonstrating hole mobilities with greater resilience to SL disorder providing potential candidates for future prototyping