The influence of plasma etching on trap levels in InP

Electroreflectance (ER) and deep level transient spectroscopy (DLTS) were carried out to characterize the effects of CF₄ plasma etching on defect levels in InP. Different chamber gas pressures were conducted to study effects on the etching result. Similar ER spectra were obtained from the starting InP wafer and the wafer after plasma etching plus rapid thermal annealing (RTA) which showed good restoration of material properties by RTA. Two impurity of structural related features, T1 and T2, were observed from these ER spectra at energy positions about 0.112 and 0.178 eV below bandgap. Two trap levels, El and E2, with activation energy 0.15 and 0.55 eV, were detected from the initial wafer by DLTS. Trap El may correlate with the Tl and T2 levels observed by ER. Similar traps were found in plasma etched samples after rapid thermal annealing with one of the DLTS peaks labeled E2 shifted to the higher temperature side as the plasma etching chamber pressure increased. We identified El to be a residual electron trap from material growth and E2 to be an interface trap arising from Schottky diode fabrication.