Nucleation of High-Field Domains in n-GaAs

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Abstract
Multiple high-field domains have been observed with a capacitive probe in relatively long samples (700∼1100 µ) ofn-GaAs with the resistivity of about 3 \varOmega-cm at room temperature. They usually appear during the first cycle of the current oscillation if the bias voltageVbis applied abruptly (dVb/dt\gtrsim1×1012V/s). While moving toward the anode, the most dominant one among them survives as a single domain in a few nanoseconds. From the comparison between the two kinds of contacts, it is deduced that the cathode contact is not essential to domain nucleation, but its inhomogeneity often gives rise to domain nucleation. In certain samples, anomalous time-dependent current saturations and large voltage drops appearing close to the cathode have been observed below the current instability threshold. They are well explained by the presence of large contact inhomogeneities.