Project Overview

Motivation

Antimony-based type-II superlattice (T2SLs) offer advantages for MWIR (Midwave Infrared) and LWIR (Long-Wave Infrared) laser and detector applications due to their broad bandgap tunability and material uniformity.  The performance of T2SL IR detectors is predicted to be superior to that of MCT (HgCdTe) IR detectors.  Recent intensive research on novel T2SL structures has demonstrated significant progress and interesting device physics, but the predicted high performance has yet to be realized as T2SL IR detectors are still limited by defects and interface-related traps.  A thorough understanding of defect physics, growth processes, and detector theory is crucial for the suppression of defect formation and their adverse effects.

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Objectives

Given the motivation for this project, the main objectives are:

1. Identify and understand the origin of point defects, line defects, interfacial traps, and surface states in T2SL structures through experimental studies closely coupled to theoretical modeling.
2. Correlate defect properties with device performance as a function of operating temperature, including minority carrier lifetime, detector noise, dark current, breakdown voltage, shunt resistance, and surface recombination.
3. Examine novel MBE and MOCVD growth methods and passivation techniques that eliminate and or mitigate defects in InAs/GaSb, InAs/InGaSb, and InAs/InAsSb T2SLs.
4. Develop a comprehensive device physics model that includes extrinsic material properties to accurately predict device performance and provide vital device design rules.

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Approaches

The specific research activities for this team include:

1. Carry out in-depth studies of the physical origins of the defects as well as their structural, electrical, and optical properties.
2. Utilize advanced in-situ and ex-situ tools and methods to study and probe T2SL defects during growth, on as-grown structures, and in fabricated devices.
3. Study surfactant mediated growth, graded interfaces, short-period superlattice buffers, post-growth treatment, H₂-implant passivation, and surface passivation.
4. Investigate and minimize the impact of defects on the performance of lasers and detectors through optimizing active layer thickness, barrier placement, and doping profile.
5. Fabricate and characterize T2SL structures and devices to provide the device and materials parameters necessary for current and next generation device modeling work.