GaAs/AlGaAs quantum well intermixing using high-density argon plasma

Abstract

We report the Ar plasma induced quantum well intermixing technique for bandgap modification of GaAs/AlGaAs quantum well structures. The application of Ar inductively coupled plasma enhances the intermixing via the energetic ion bombardment mechanism and the effect of high plasma density. A bandgap shift up to 39.6 meV (20.5 nm) with a linewidth broadening of 4.2 meV (1.5 nm) was obtained. The bandgap shift was observed to saturate with increasing plasma exposure time in good agreement with the theoretical model that most beneficial point defects are introduced at the early exposure stage. To further reveal the mechanism of intermixing, the plasma-induced damage distribution range was investigated after exposure and subsequent annealing using a structure of GaAs/AlGaAs quantum wells of different well widths as a highly sensitive damage probe. The result indicates that the point defects are created near the sample surface during Ar plasma exposure and upon annealing they propagate downwards from the surface to promote quantum well intermixing to a depth beyond ∼2.32 µm.