Growth mechanisms of GaN on the O-terminated ZnO(000-1) surfaces

We have investigated the stability of the 1ML-GaN on the O-polarity ZnO(000-1) interface structure using the first-principles calculation. We have found in our calculated results that the most stable structure for the 1ML-GaN on the O-polarity ZnO(000-1) interface has the N-polarity. However, we have found that the results of the adatom dynamics on the O-terminated ZnO(000-1) surface shows the Ga-polarity. We find that the key to change the polarity of GaN crystal grown on the O-terminated ZnO(000-1) surface is the growth temperature. We have suggested that the optimized initial growth condition for the growth of the Ga-polarity GaN crystal on the O-terminated ZnO(000-1) surface is under the suitable low temperature and the stoichiometric growth condition. Experimental observations show that GaN grown on ZnO(000-1) by PLD at substrate temperatures below 300C has Ga-polarity, which is quite consistent with the theoretical calculations