ABSTRACT
We have developed a system for viewing regions of high electric field in semi-insulating GaAs under bias at variable temperature. This method utilizes imaging the transmission of near-bandedge light. Changes in transmission result from absorption that is induced by the Franz-Keldysh effect.
We have used the system to investigate electrical breakdown in materials similar to those that are to be used in nuclear particle detectors. Although the electric field at room temperature contains a stable component, it also exhibits moving domains which appear to be due to field enhanced electron trapping. However, these domains are not seen at low temperatures. Below a temperature about 200K, slowly moving high electric field domains are seen which are consistent with field enhanced trapping of holes.
