Capacitance dispersion in n-LT-i-p GaAs structures with the low-temperature layers grown at different temperatures

The electrical properties of annealed low-temperature GaAs are studied by i nvestigating the frequency-dependent capacitance of n-LT-i-p structures wit h the low-temperature (LT) layers grown at different temperatures. Relative to the sample grown at 610 degrees C, the samples grown at 200, 300 and 40 0 degrees C show significant capacitance dispersions over frequency which i s explained by the emission of carriers from traps. Based on a proposed ban d diagram where a dominating trap at 0.66-0.74 eV exists in the LT layers, the high-frequency dispersion is shown to be affected by resistance-capacit ance (RC) time constant effects. From the mid-frequency capacitance versus voltage characteristics, the concentrations of the occupied traps are estim ated to be approximate to 10(17) cm(-3) for samples grown at 200, 300 and 4 00 degrees C, which are found to be consistent with those obtained from ana lyzing the current-voltage characteristics of n(+)-LT-n(+) structures.