A critical analysis of capacitance transient signals due to DX centres in n-type AlGaAs

In n-type AlGaAs layers, the evolution of high frequency capacitance with time due to electron emission from DX centres has been computer simulated. The electron density profiles during the emission and capture processes are also presented. The effects of switching voltage amplitude and DX level position in the gap have been considered. A critical discussion of the signals obtained, the intrinsic sources of non-exponentiality and the reliability of the DX parameters extracted, are presented. The artifacts due to the DLTS processing of the capacitance transients generated were also considered. The subject of alloy broadening has been addressed, and it has been unambiguously shown that intrinsic broadening may only account for less than half the measured broadening in Al_0.3Ga_0.7As:Si.