Hole intersubband transitions
This project focuses on the fundamental understanding of the physics of hole intersubband transitions and of ultrafast hole relaxation processes in high-purity GaAs/AlGaAs heterostructures grown by Molecular Beam Epitaxy (MBE). Experimental measurements and detailed modeling of intra-valence band transitions are performed to identify the unique optical properties of Carbon-doped GaAs/AlAs heterostructures. Hole intersubband transitions are particularly interesting for their potential to enable true surface emitting lasers operating in the mid-infrared range of the electromagnetic spectrum. This project investigates the feasibility of a novel quantum cascade laser utilizing intersubband transitions in the valence band. It also allows an evaluation of the impact of material issues on quantum cascade laser performance. The knowledge acquired is relevant not only to lasers and detectors based on GaAs/AlAs but also to devices utilizing other semiconductor systems such as InGaAs/InAlAs, Si/SiGe, and GaN.