Degradation analysis and current collapse imaging of AlGaN/GaN HEMTs by measurement of electric field-induced optical second-harmonic generation

On the basis of electric field-induced optical second-harmonic generation (EFISHG) measurements, the degradation of AlGaN/GaN high electron mobility transistor (HEMT) devices was analyzed and the current collapse phenomenon was imaged. Strong second-harmonic (SH) signals were observed at the gate edge at the site of a small defect during the application of a high drain stress voltage (300 V), thus indicating that this technique can identify degradation of HEMTs. The EFISHG technique also generated images of the trapped carriers that lead to current collapse in these devices during the on-state. Immediately following the completion of drain-stress voltage application in the off-state (that is, 1 mu s), SH signals were observed at the gate edge on the drain electrode. This signal location is in good agreement with the well-known virtual gate model of current collapse. The EFISHG measurement technique is therefore capable of detecting pre-breakdown phenomena and producing images of current collapse in AlGaN/GaN HEMT devices. (C) 2014 Elsevier Ltd. All rights reserved.