Electrical properties of N-polar Si-doped GaN prepared by pulsed sputtering

Abstract

We have demonstrated the homoepitaxial growth of N-polar GaN and its Si doping by pulsed sputtering deposition (PSD). Enhanced surface migration by a pulsed supply of precursors enabled the step-flow growth on N-polar GaN bulk substrates even with small miscut angles. The relationship between electron concentration and mobility in N-polar GaN follows the Caughey–Thomas relationship for Ga-polar GaN, which indicates PSD N-polar GaN has a low concentration of scattering centers. N-polar heavily Si-doped GaN film yielded a record-low resistivity of 1.6 × 10−4 Ωcm with an electron concentration of 3.6 × 1020 cm−3 and mobility of 109 cm2V−1s−1, comparable to the best data for Ga-polar GaN. The high electron mobility can be attributed to the reduced concentration of compensating acceptors, which is also consistent with its optical measurements. Moreover, optical measurements show that the Burstein–Moss effect raises the Fermi level by 0.2 eV. These results show that heavily Si-doped N-polar GaN prepared by pulsed sputtering is promising for future applications such as the source/drain of high-performance N-polar GaN HEMTs.