Simulation of capacitance-voltage profiles for the analysis of measurements at a p-type Si-SiGe-Si single quantum well

Simulations of apparent doping profiles as obtained from C-V measurements at pn or Schottky diodes are used to analyse data measured at a Si-SiGe-Si single quantum well device. C-V characteristics are simulated by numerically solving Poisson's equation for a multilayer structure using the algorithm of Rimmer, Missous and Peaker (1991). Some refinements are given to improve the precision and stability of this method. The valence band offset for a SiGe layer (4% Ge content) on a Si substrate is deduced from temperature-dependent C-V measurements to be Delta E=25-30 meV. The main accuracy-limiting factor for a band offset determination from C-V measurements is the influence of doping inhomogeneities, but the error can be reduced by taking into account C-V profiles measured at different temperatures.