Characterizing electric fields in semiconductor devices: effect of second-harmonic light interference.

Characterizing electric fields in semiconductor devices using electric field-induced second-harmonic generation (EFISHG) has opened new opportunities for an advanced device design. However, this new technique still has challenges due to the interference between background second-harmonic generation (SHG) and EFISHG generated light. We demonstrate that interference effects can effectively be eliminated during EFISHG measurements by focusing the laser from the transparent substrate side of a GaN PN diode, enabling straightforward quantitative electric field analysis, in contrast to PN junction interface side measurements. A model based on wave generation and propagation is proposed and highlights the incoherence between background SHG and EFISHG light. This incoherence may be attributed to the depth of focus of the incident laser and phase mismatch between incident and SHG light.