Measurement of the Surface Electrical Potential in a Planar Avalanche Photodiode Near Breakdown

The surface voltage profile of an avalanche photodiode has been measured by monitoring the energy shift of the indium MNN Auger transition as a function of position across the junction in a scanning Auger microprobe. The surface electric field at the p‐n junction was found to be when the diode was biased just below breakdown. A small drop across the p − guard ring was also observed and confirmed with electron beam‐induced current. The voltage drop indicated that the diode depletion layer extended across the guard ring. The excellent spatial resolution (0.2 μm) and voltage precision (± 2V) achieved in this study demonstrate the value of this technique for measuring high surface electric fields in planar devices.