Influence of rapid thermal annealing on modulation doped structures

Abstract We have investigated the influence of high temperature annealing on modulation doped structures of AlGaAs/GaAs, AlGaAs/InGaAs and InAlAs/InGaAs systems grown by molecular beam epitaxy. Hall-measurement reveals reduction in two-dimensional electron gas mobility and almost unchanged sheet density after annealing at 800–880°C for 5 s in each hetero-junction system. The mobility reduction is enhanced with the increase in annealing temperature and with the decrease in thickness of a spacer between a donor layer and a channel layer. This behavior is attributed to diffusion of Si dopants from a donor layer to a spacer layer resulting in an increasing ionized impurity scattering effect. It is found that In contained structures especially an InP-based InAlAs/InGaAs structure, provide both large 2DEG sheet density and excellent thermal stability of the modulation doped structure.