Long relaxation times of holes in Si/SiGe quantum cascade structures with a diagonal intersubband transition

Continuous Voltage Tunability of Intersubband Relaxation Times in Coupled SiGe Quantum Well Structures Using Ultrafast Spectroscopy

“…Quantum cascade lasers (QCLs) are based on intersubband transitions [4], and this type of transition provides tremendous control over the state energies and wave functions, and hence on overlaps and lifetimes. Modifying the design of the structure from spatially direct to indirect (diagonal) radiative transitions in QCL structures provides a means of increasing the lifetime of the excited state over many orders of magnitude, in order to achieve population inversion and lasing [5][6][7]. Although control via structural design is attractive, voltage control of the lifetime within a single structure offers a way to perform novel dynamics experiments and has potential benefits for understanding incoherent laser dynamics.…”