Indium nitride (InN) is a prominent semiconductor material with the lowest effective mass, the highest mobility, and the highest saturation velocity in group-III nitrides. In addition, the revised bandgap value (0.7 eV) of InN has opportunities for implementing high-efficiency InN photovoltaic devices. Therefore, InN has highly potential applications for high speed, high frequency electronic device and high-efficiency photovoltaic devices. Since silicon (Si) is still a major material in semiconductor device, the integration of InN on Si(111) opens a new path toward advanced devices. However, the performances of InN/Si on electronic and photovoltaic devices are lower than prediction. In this study, the auto-doping effect on InN/Si heterojunction is investigated to explain the reason affected on electronic characteristic.

InN film was grown on silicon substrates at growth temperature of 450 °C in 10-11 torr by plasma assisted molecular-beam epitaxy (PA-MBE) with a radio frequency (RF) nitrogen plasma source. From FESEM and TEM morphology, InN/p-Si is less compact than InN/n-Si. Exactly, the pore size of InN/p-Si and InN/n-Si are in the range of 100 - 300 nm and 50 - 150 nm, respectively. Thus, Hall mobility of InN/n-Si is higher than InN/p-Si. From Synchrotron Radiation Photoemission Spectroscopy (SR-PES) results, InN/p-Si and InN/n-Si are a type-II heterojunction and a type-III heterojunction, respectively. However, the auto-doping effect in InN/n-Si is more apparent than in InN/p-Si from X-ray photoelectron spectroscopy (XPS) and Auger Electron Spectroscopy (AES) results. From SR-PES and I-V results, InN/p-Si exhibits a diode characteristics and InN/n-Si is an ohmic contact. From the capacitance measurement, the interface carrier density can be deduced.

In conclusion, the auto-doping effect on InN/n-Si(111) is more apparent than InN/p-Si(111), which affects the further electronic characteristics and applications. The electron accumulation on InN grown on n-Si(111) is serious as a result of more interface states originated from auto-doping effect. Therefore, the InN grown p-Si(111) is recommended to further advanced applications.

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