Real Time Imaging of Propagating High Field Domains in Semi-Insulating GaAs
Semi-Insulating (SI) GaAs shows spontaneous current oscillations when a DC bias voltage in the order of 1 kV/cm is applied, related to the formation of high field domains. This self organized structure is commonly explained by a negative differential resistance due to field enhanced capture of electrons, presumably in EL2 traps. Although a model has been elaborated since 19701, many input parameters and their dependence on electric field, which are generally poorly known, must be introduced. Measuring only current and voltage at the electrodes does not provide for sufficient information for any quantitative description. Therefore we present results obtained with a time resolved, non-invasive technique that allows a quantitative measurement of the voltage profile for a domain traveling in the sample. From those measurements, we obtain all the necessary information relevant for the description of the domain structure, and have direct access to the electric field dependence of the trapping coefficient, which is the origin of the domain formation.
KeywordsTrap Electron High Electric Field Emission Coefficient Negative Differential Resistance Voltage Profile
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