Studies of Electron Traps in Gallium Arsenide and Gallium Arsenide Phosphide by Deep Level Transient Spectroscopy

160 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1980.System effects and data analysis for deep level transient spectroscopy (DLTS) have been examined and applied to study the deep levels in the GaAs-GaP system.Studies of typical DLTS systems using either the lock-in amplifier or the dual-channel boxcar averager are presented. The effects of non-zero gate width for the boxcar averager, phase angle adjustment for the lock-in amplifier, and response time of a typical commerical capacitance meter are investigated. Errors introduced in the measurements by these effects are calculated for typical cases. Measurements of the gold level in silicon are presented, along with calculated corrections. We find the correction to be minimal in the boxcar-averager method, but significant in the lock-in amplifier approach.A DLTS system is described for measuring deep levels in diodes exhibiting large leakage currents. A capacitance bridge is used employing the diode to be tested along with a dummy diode of similar characteristics. The DLTS spectrum of a leaky GaAs planar diode is measured and compared to experimental results obtained with two standard DLTS systems. It is shown that measurements with the standard systems are impossible in certain temperature ranges because of overloading problems. The approach described here, however, gives the DLTS spectrum between 77(DEGREES) and 300(DEGREES)K.In the study of the main electron trap (0.83eV from the conduction band) in VPE n-GaAs, we have examined the annealing behavior of this deep level and the effect of the implanted species. In the annealing study, we find that the trap concentration change is related to the Ga vacancy. In the implantation study, we observed that the trap concentration changes depending on whether the implanted species is incorporated into Ga or As substitutional sites. The DLTS results suggest that the main electron trap involves the Ga vacancy.Electron traps in VPE n-GaAs(,1-x)P(,x) alloys with several compositions have been examined. It is observed that the DLTS spectra for the as-grown alloys are similar to each other. There are differences in DLTS spectra among the N-doped, N-free, and N-implanted samples for the same alloy composition. Deep levels caused by the radiation-induced damage are observed in the N-implanted samples.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD