Photoelectric characteristics of metal/InGaN/GaN heterojunction structure

A heterojunction structure photodetector was fabricated by evaporating a semitransparent Ni/Au metal film oil the InGaN/GaN structure. The photocurrent (PC) spectra show that both the Schottky junction (NiAu/InGaN) and the InGaN/GaN isotype heterojunction contribute to the PC signal which suggests that two junctions are connected in series and result in a broader spectral response of the device. Secondary electron, cathodoluminescence and electron-beam-induced current images measured from the same area of the edge surface clearly reveal the profile of the layer structure and distribution of the built-in electric field around the two junctions. A band diagram of the device is drawn based oil the consideration of the polarization effect at the InGaN/GaN interface. The analysis is consistent with the physical mechanism of a tandem structure of two junctions connected in series.

National Natural Science Foundation of China 60506001 604760216057600360776047National Basic Research Program 2007CB936700 The authors are grateful to Dr Uwe Jahn for the SEM measurements and illuminating discussions. This work was supported by the National Natural Science Foundation of China (Grant Nos 60506001, 60476021, 60576003 and 60776047) and the National Basic Research Program (2007CB936700).