Effect of Magnetic Fields on Impact Ionization Rates and Instabilities in InSb

The effect of magnetic fields on the avalanche plasma production rate in n-type InSb and the resulting instabilities was measured. It was found that the magnetic field decreased the carrier generation rate, but the amount of decrease varied with the applied electric field. Longitudinal and transverse magnetic fields appear to affect the generation rate in the same manner and to the same degree. The generation rate most closely fits an electric field dependence of the form g(E) exp(-kE) for moderate fields. The dependence of the generation rate on electric field is compared with existing theories. For essentially constant current conditions, a plasma instability characterized by a sharp drop in voltage across the sample is observed. The current threshold of instability is found to decrease with applied longitudinal magnetic fields. For transverse magnetic fields, the current threshold increases initially and then decreases with maximum threshold current observed for a field of 500 G. Both orientations of the magnetic field reduce the magnitude of the voltage decrease.