Surface reconstruction patterns of GaN grown by molecular beam epitaxy on GaN bulk crystals

An investigation of the conditions giving rise to surface reconstruction fo r GaN grown by molecular beam epitaxy on (0 0 0 (1) over bar) bulk GaN subs trates has been carried out. The results of different surface reconstructio ns were investigated by supplying Ga and active nitrogen separately to GaN surfaces. A (2 x 2) reconstruction on (0 0 0 (1) over bar)GaN substrates an d for GaN layers grown on such substrates was observed. The (2 x 2) surface reconstruction is stable in the presence of an active nitrogen flux at hig h temperature, but it disappears on cooling the GaN sample below similar to 400 degrees C. The (2 x 2) reconstruction is considered to be due to an ad ditional amount of relatively tightly bound Ga on this (1 x 1) surface. Add ing further Ga to the (2 x 2) reconstructed surface resulted in a return to a (1 x 1) reconstruction. (C) 1999 Elsevier Science B.V. All rights reserv ed.