Unintentional Fe incorporation in the homo-epitaxy of GaN on Fe-doped freestanding GaN substrate

Abstract The unintentional Fe incorporation in the homo-epitaxy of GaN on Fe-doped freestanding GaN substrate is harmful to the performance of a high-electron-mobility transistor device, but the incorporation mechanism is unclear. The memory effect, diffusion from the Fe-doped GaN substrate to the epilayer, thermal decomposition on the N-face and Ga-face are all considered to find the origin. The Ga-face thermal decomposition during the heating process before growth is regarded as the main reason responsible for the unintentional Fe doping according to the time-of-flight secondary ions mass spectroscopy measurement results, vapor phase decomposition inductively coupled plasma mass spectrometry, and dynamic secondary ions mass spectroscopy measurement results. Molecular beam epitaxy growth of the GaN epilayer at lower temperatures could effectively suppress the unintentional Fe doping.