RHEED studies of group III-nitrides grown by MBE

We report on the mechanisms giving rise to surface reconstruction for homo- epitaxial GaN grown by molecular beam epitaxy on (000 (1) over bar) bulk Ga N substrates. We:have studied the surface reconstruction observed during gr owth and investigated the effects of supplying Ga and active nitrogen separ ately to the GaN surface. During growth we can observe a (2 x 2):reconstruc tion on (000 (1) over bar) GaN under appropriate conditions. We have observ ed a (2 x 2) reconstruction on the GaN(000 (1) over bar) substrates induced by supplying Ga to that surface. We have shown that the (2 x 2) surface re construction is stable in the presence of an active nitrogen flux at high t emperature, but it disappears on cooling the GaN sample below approximate t o 400 degrees C. Finally, we propose: two possible growth models for GaN wh ich can explain our RHEED data.