AlN grown on a- and n-plane sapphire substrates by low-pressure hydride vapor phase epitaxy

We have studied the properties of AlN layers grown by low-pressure hydride vapor phase epitaxy (HVPE) on n-plane (11-23) sapphire substrates and compared them with those of AlN layers on a-plane (11-20) sapphire substrates. c-Plane AlN was grown on a-plane sapphire. In the case of AlN growth on n-plane sapphire, the c-axis of AlN was tilted by about 1.2° relative to the n-axis of sapphire, unlike AlN growth on a-plane sapphire. For AlN grown on a-plane sapphire, the in-plane epitaxial relationship between AlN and sapphire changed with nitridation temperature in the initialstage of growth, but it remained constant for AlN grown on n-plane sapphire.