Detailed electrical characterization of DX centers in Se-doped AlxGa1−xAs

Abstract

DX centers in selenium doped AlxGa1−xAs with two values of the aluminum content, x=0.34 and 0.48, are carefully analyzed by three different techniques: deep level transient spectroscopy (DLTS), admittance spectroscopy, and the capacitance voltage transient technique (CVTT). We use conceptual differences between these techniques to extract important information about the nature of the DX centers. Good agreement is found between the capacitance transients recorded during the DLTS measurements and those obtained by CVTT at every point in the space charge region. From that, we conclude that is the very nature of the DX centers the solely responsible for the anomalies found in DLTS results. The main cause for these anomalies is the thermal dependence of the electron capture rate of these centers. CVTT curves also reveal that no electric field enhanced emission processes take place for these centers. For our analysis of the shape of the DLTS and admittance spectroscopy curves we conclude that several DX levels exist, according to the alloy broadening theory. Finally, some simulations of the DLTS spectra were made. These calculations reveal the important effect of experimental parameters such as the filling pulse duration, the velocity of the temperature scan, and the initial conditions of the occupation factor of the deep levels on the DLTS curves.