Fourier transform infrared spectroscopy of 6.1-Angstrom semiconductor quantum wells
Master of Science thesis
The 6.1-Angstrom (A) family of III-V semiconductors---InAs, GaSb, and AlSb and their alloys and heterostructures---has unique properties that may find application in next generation multi-functional semiconductor devices. In this project, we investigate intersubband transitions in 6.1-A quantum wells. The short-term objective is to explore high-photon-energy (or short-wavelength) intersubband transitions that are expected to occur in these systems due to their extremely large conduction-band offsets. The ultimate goal of this project is to construct a solid-state terahertz (THz) emitter based on 6.1-A quantum wells under intersubband pumping. We have established reliable and reproducible sample preparation methods for measuring intersubband transitions using Fourier-transform infrared spectroscopy. In particular, we observed intersubband transitions in 6.1-A quantum wells in a previously unexplored short-wavelength range. We systematically studied intersubband transition energies, intensities, and linewidths as functions of well width and temperature, and compared the results with calculations based on an 8-band k·p theory. Experimental methods, experimental results, and discussion will be presented in detail. Furthermore, transmission electron microscopy (TEM) was used to assess the quality of interfaces in 6.1-A quantum wells. A description is given for the sample preparation procedure together with some TEM pictures.
Engineering, Electronics and Electrical; Physics, Condensed Matter; Physics, Optics