Out-of-plane Excess Carrier Density Variations in Point Contact Lattice-based test Structures for QSSPC Contact Recombination Current Measurements

We discuss the effect of out-of-plane excess carrier density variations on contact recombination currents extracted from quasi steady state photoconductance (QSSPC) measurements on a dedicated test structure. The test structure features lattices of point contacts. The contacts are thick and non-transparent. Therefore, asymmetric test structures are generally used to ensure a homogeneous in-plane generation rate. As a result, the QSSPC measurements are relatively prone to out-of-plane excess carrier density variations. Their effect on the extracted contact recombination characteristic is discussed theoretically and the theory is confirmed by experiment. The resulting framework contributes to the set of design rules and best practices for contact recombination current characterization using QSSPC measurements on point contact lattice based test structures.