Improved electrical properties of N-polar GaN grown via MOVPE with TMGa pulsed supply method

This study introduces a pulsed precursor supply method in the metalorganic vapor phase epitaxy (MOVPE) is introduced to address the issue of high-concentration residual impurities (C, O, H) incorporated into N-polar GaN during growth at low-temperature and high-V/III ratio conditions. Four different pulsed supply methods were compared in terms of their effect on crystal quality and electrical properties: alternating supply of trimethylgallium (TMGa) and ammonia (NH 3 ), TMGa pulsed supply, NH 3 pulsed supply and continuous supply. The results confirmed that the TMGa pulsed supply method improves surface flatness, suppresses lattice relaxation, and enhances electrical properties such as increased carrier mobility. In contrast, the NH 3 pulsed supply method induces three-dimensional growth and severe crystal relaxation, significantly degrading the electrical performance. Furthermore, optimizing TMGa OFF duration showed that shorter TMGa OFF durations are effective for improving surface morphology and electrical properties, reducing the O concentration by an order of magnitude compared to the conventional continuous supply method. These results demonstrate that the TMGa pulsed supply method, with an appropriate pulse interval, is effective for achieving high-quality and high-performance N-polar GaN