Electric-field-induced second-harmonic generation in GaN devices.

Electric-field-induced second-harmonic generation is used to detect electric fields in a GaN UV Schottky photodiode and in a GaN light-emitting diode. The second-harmonic signal is measured as a function of bias voltage and incident laser power. This technique is sensitive to small applied voltages and can be used to track electronic waveforms. The photocurrent generated by this technique is found to be less than 100 pA when the fundamental and second-harmonic frequencies are both below the device bandgap.