Temperature dependent capacitance-voltage analysis of unintentionally doped and Si doped Al_0.82In_0.18N grown on GaN

Unintentionally doped (UID) and Si doped Al_0.82In _0.18N samples were grown on Si-doped GaN by metalorganic chemical vapor deposition. The high structural quality of the Al_0.82In _0.18N layers was confirmed by high resolution X-ray diffraction and transmission electron microscopy. Secondary ion mass spectrometry measurement showed oxygen levels of (2-6) × 10¹⁸cm^-3 regardless of the explored growth conditions. Vertical Schottky diodes were fabricated with a Pd-based Schottky contact on Al_0.82In_0.18N and Ti/Al/Ni/Au-based ohmic contact on n-type GaN. Capacitance-voltage (C-V) analysis showed that UID Al_0.82In_0.18N was an n-type with a carrier density of about 3 × 10¹⁷ cm^-3 in the bulk region at 300 K. Based on the temperature dependent C-V analysis from 100 to 300 K, the donor activation energy was found to be 4meV, showing very weak temperature dependence despite the large bandgap of Al_0.82In _0.18N. Si-doped Al_0.82In_0.18N ([Si] ≈ 2 × 10¹⁸ cm^-3) showed almost no carrier freeze-out at carrier density of 1.0 × 10¹⁸ cm^-3.