Selective area growth of GaN on trench-patterned nonpolar bulk GaN substrates
Anisotropic structures are formed after reactive-ion etching.
Lateral growth rate increased for trench pattern at 45° off from the a-axis.
Smooth (10-10) surface obtained for miscut angles of substrates at 1°.
Selective area growth of GaN (SAG-GaN) films grown on nonpolar m-plane bulk GaN substrates using trench patterns was performed by metalorganic vapor phase epitaxy. We investigated the transformation of SAG-GaN facet structures by changing growth temperature, ambient, and miscut angle of substrates. Substrates with trench patterns along a-axis formed (10-11), (10-10), and (000-1) facet structures after SAG-GaN growth for growth conditions of 800 °C in N2+NH3 and 1000 °C in H2+NH3 ambience. Those with trench pattern along 45° off from a-axis contained (11-22), (10-10), (0-110) facet structures in substrates with a miscut angle of 5° whereas SAG-GaN films completely coalesced and formed smooth (10-10) surface in substrates with a miscut angle of 1°. Undesirable grains were formed for 800 °C in N2+NH3 ambience regardless of the miscut angle of substrates whereas theses grains were annihilated using 1000 °C in H2+NH3 ambience due to the intensively hydrogen etching.