Mapping of differently doped InP wafers by nanosecond and picosecond four-wave mixing techniques

Abstract

Time-integrated and time-resolved FWM techniques were applied for characterization of the photoelectrical properties of undoped, S-doped, and Fe-doped InP wafers and for a mapping of their homogeneity. We performed measurements of spatial distribution of diffraction efficiency across the wafers by nanosecond FWM and investigated a physical origin of the observed variations by using time-resolved picosecond FWM. By analyzing the diffraction efficiency kinetics and its dependence on excitation energy, we evaluated the impurity-assisted carrier generation, recombination, diffusion processes, electrical activity of the defects, and their distribution across the wafers. Carrier lifetime variation from 2.5 ns to 7.5 ns across the undoped InP wafer was found, while the diffusion coefficient value of 8 ± 0.5 cm2/s was almost constant. In S-doped InP wafer, wafer inhomogeneity was attributed to carrier generation peculiarities governed by spatial distribution of deep centers.