GaAs wafer mapping by microwave-detected photoconductivity

An improved highly sensitive method of detecting photo conductivity by microwave absorption (MDP) is described. The method is applicable to semi-insulating and low resistivity marterial as well. It is non-destructive and can be applied to epi-layers. MDP topograms are compared with those for photo luminescence, point contact, and EL2 using the same sample. The MDP-contrast is mainly due to a so far unknown recombination centre determining the carrier lifetime under non-equilibrium. The annealing behaviour of MDP is very similar to that of the point-contact method. In general, MDP has the potential to be used as a new tool for material quality inspection with direct evidence for device properties.