Influence of thermal annealing on the electron mobility in modulation doped Si/SiGe heterostructures

Abstract

We grew n-type modulation doped Si/SiGe multiple quantum well structures with the highest electron mobilities reported so far for this heterosystem. The samples were annealed at temperatures between 750 and 950 °C for 1000 s and subsequently characterized by x-ray rocking analysis, secondary ion mass spectroscopy, and temperature dependent Hall measurements. A moderate decrease in room temperature Hall mobility is observed up to annealing temperatures of 900 °C. Above 900 °C the samples become homogeneously doped and show strong Si/Ge interdiffusion at the heteroboundaries. The annealing effects are discussed in terms of dopant and Ge diffusion, and of metastability of the SiGe layers.