Microwave Measurement of the Velocity-Field Characteristics in n-Type Gallium Arsenide

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Abstract
In order to clarify the reasons of large conflict in the velocity-field characteristics of GaAs among many experiments reported so far, the effects of nonuniform conductivity and low-field mobility on the velocity-field characteristics are investigated using a microwave-heating technique. Various degrees of nonuniformity are introduced by serial irradiation of electrons on a localized portion of the sample. The results show that the threshold field, peak velocity and negative differential mobility increased with increasing the nonuniformity. The initial value of the negative differential mobility is typically -1660 cm2/vo1t·sec, but it decreases down to -920 cm2/volt·sec after the local electron typically irradiation. Low-field mobility was changed by a uniform irradiation of the sample. As the low-field mobility is decreased, the threshold field increases while the peak velocity and negative differential mobility decreases, as will be predicted from the theory. Some facts supporting the occurrence of the impact ionization of irradiation-induced defects are obtained.