X. Theodore Zhu

Electron mobility enhancement by confining optical phonons in GaAs/AlAs multiple quantum wells

We report experimental evidence for an enhanced electron mobility in a multiple quantum well structure in which the optical phonon modes are confined. By inserting n ultrathin layers of AlAs into a host GaAs well, thus dividing the bulklike host well into n+1 miniwells, we observe a substantial enhancement in electron mobility for temperatures T≳100 K. We have also studied the dependence of the electron mobility on the miniwell width. The electron mobility is found to first increase with decreasing miniwell width and then decrease after reaching a maximum value at the width around 45 A.

Enhancement of Mobility in Pseudomorphic FET's with Up and Down Monolayers

We have used molecular beam epitaxy (MBE) to grow single molecular layers (monolayers) in quantum wells in order to improve electron transport. The quantum well energy levels, wave functions, and the carrier concentrations are obtained by self-consistently solving the Schrodinger and Poisson equations. Photoluminescence (PL) and Hall measurements confirmed the energy level shifts and the mobility enhancement due to the monolayer insertions.