Nucleation of High-Field Domains in n-GaAs

Abstract

Multiple high-field domains have been observed with a capacitive probe in relatively long samples (700∼1100 µ) of n-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 voltage V b is applied abruptly (d V b /d t\gtrsim1×1012 V/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.

Investigation of Surface Breakdown on Semiconductor Devices Using Optical Probing Techniques.

“…There is a propagating density disturbance which corresponds to the high-field domains in the electric field profile. Figures 25 and 28 are consistent with previous calculations [44] and experiments [45] for GaAs Gunn diodes.…”

Experimental assessment of anomalous low-frequency noise increase at the onset of Gunn oscillations in InGaAs planar diodes

“…Other effects such as self-mixing were discarded as origin of the ALFN, since the separation between the highfrequency peaks is significantly larger (several GHz) than the frequency around which it concentrates. On the other hand, inhomogeneities at the cathode contact leading to saturated I-V curves, [14][15][16] like those exhibited by our devices, could also be at the origin of a noise enhancement in diodes not exhibiting oscillations unless connected to a resonant circuit. 10 However, this does not seem to be the origin of the effect we observe, since: (i) simulations of diodes with ideal contacts show a very similar noise enhancement, 8 (ii) measurements in diodes exhibiting a standard Gunn-like I-V curve (with negative differential resistance) show also indications of a noise increase at low frequencies.…”