EBIC CHARACTERIZATION OF BULK GAAS - TEMPERATURE-DEPENDENCE OF THE DIFFUSION LENGTH AND OF THE SPACE-CHARGE REGION WIDTH

EBIC charge collection efficiency curves as a function of beam accelerating voltage are recorded at 300 and 77 K from a n-type GaAs bulk specimen. The influence of the generation function on parameters determination, such as diffusion length, L, and doping level are discussed as well as the accuracy of the method. Experimental curves are well fitted when recombination in the space-charge region (SCR) is assumed, and when the appropriate generation function is introduced in the calculations. From the decrease of L with temperature, which is area dependent, it is suggested that L is controlled by deep levels at 300 K and by shallow levels at 77 K. A deviation of the curves is observed when recorded at 77 K by decreasing the accelerating voltage. This is explained by the presence of a double deep level in the SCR, whose ionisation state is modified during the experiment.