Spectroscopy of III-V narrow gap semiconductor quantum wells

[摘要] The narrow gap III-V semiconductors, InAs/AlSb/GaSb and InSb, exhibit an array of extreme physical properties, from the lightest effective mass and largest nonparabolicity of III-V semiconductors to heterostructure conduction band offsets ranging from -0.15 to +2.0 eV. In this work, I present three spectroscopic techniques which exploit these unusual properties to provide new insight into the physics of these materials. First, my measurement of cyclotron resonance in InAs/AlSb and InSb/AlInSb quantum wells was the first spectroscopic application of a new laser, the THz quantum cascade laser. The physical properties mentioned above put these materials into an experimentally accessible range, and InAs;;s high room temperature mobility and low temperature carrier density enabled us to explore a large temperature range. Previous investigations of other materials in limited temperature ranges had suggested what we confirmed: the cyclotron resonance effective mass increases with temperature, contrary to theoretical expectations. Second, we applied time resolved cyclotron resonance to InSb quantum wells for the first time. Because of InSb;;s large effective g-factor and nonparabolicity, time resolved cyclotron resonance enabled us to monitor the carrier relaxation and recombination from each Landau- and Zeeman-quantized state directly in time. This unprecedented level of detail could be extended to longer times to probe spin-flip relaxation, a significant parasitic process in quantum computation. Finally, I measured intersubband absorption in narrow InAs/AlSb quantum wells with widths from 10.5 to 1.8 nm. I observed the highest energy intersubband resonance in InAs/AlSb quantum wells: 650 meV at 77 K in a 1.8 nm well. I also performed detailed measurements of the temperature dependence of intersubband absorption and confirmed the correlation between the integrated intensity of intersubband absorption and the carrier distribution inferred from Shubnikov-de Haas and Hall measurements. Because of InAs/AlSb intersubband transitions;; large accessible energy and temperature robustness, they are ideal candidates for resonant nonlinear optics. In particular, I discuss the potential of InAs/AlSb double quantum wells as a compact, room temperature, and coherent THz source. Such a source could revolutionize chemical sensing by providing convenient access to the strong fundamental vibrational fingerprints which all molecules have in the THz, potentially transforming applications from medicine to the military.

[发布机构] Rice University

[效力级别] Electrical engineering