InAs-based Quantum Cascade Devices on GaSb Substrates
Abstract
Quantum cascade detectors (QCD) are high-speed room-temperature photovoltaic detectors that use unipolar intersubband (ISB) transitions to detect mid-infrared (MIR) light [1]. The possible detection wavelengths are determined by the conduction band offset (CBO) between the barriers and wells and not limited to the semiconductor band gap. The optical transition levels and the carrier extraction levels are designed through band structure engineering. This allows great freedom in active region design and the ability to cover a wide range of wavelengths (energies). The InAs/AlAsySb1-y material system has a CBO of 2.1 eV at the ?-point and 1.35 eV at the L-valley. At the same time, InAs has a low electron effective mass 0.023m0, compared to InGaAs 0.043m0, and GaAs 0.067m0 quantum wells. The m*e is inversely proportional to the oscillator strength of the optical transition and thus, for InAs quantum wells, improves the absorption over InGaAsand GaAs-based ISB detectors [2]. Additionally, QCDs can be optimized to work at high-frequencies, up to 50 GHz, a result of the picosecond lifetimes of the intersubband states [3]. Due to the ISB selection rules, ISB optoelectronics are only sensitive to TM polarized light, in the growth direction. This means that ISB photodetectors need to couple in the light while still satisfying the ISB selection rules. In this project we will study the growth, design, and performance of InAs-based QCDs on GaSb substrates. Using GaSb substrates has the advantage of a relatively large substrate band gap, so that wavelengths longer than 1.7 ?m (0.726 eV) are not absorbed by the substrate. This enables a greater choice of incoupling designs, frontside/backside illumination, and diffraction gratings, while utilizing the desired InAs quantum wells and AlAsySb1-y barriers.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 21, 2022
- Source ID
- FA86552217170XX0
Entities
People
- Aaron Andrews
Organizations
- Air Force Office of Scientific Research
- TU Wien
- United States Air Force