Characteristic trapping lifetime and capacitance-voltage measurements of GaAs metal-oxide-semiconductor structures

The authors show the implications that the free carrier trapping lifetime has on the capacitance-voltage $\left(CV\right)$ characterization method applied to metal-oxide-semiconductor (MOS) structures. It is shown that, whereas the $CV$ characterization method for deducing interface state densities works well for Si, the generally used frequency range of $100\mathrm{Hz}–1\mathrm{MHz}$ is much less adapted to GaAs MOS structures. Only interface trapping states in very small portions of the GaAs bandgap are measured with this frequency range, and mainly the very important midgap region is not properly probed. Performing an additional measurement at $150°\mathrm{C}$ on GaAs MOS structures eliminates this problem.