Various reconstructions of the (00•1) surface were studied by using scanning tunnelling microscopy. On the basis of a comparison between scanning tunnelling microscopic observations and first-principles total-energy calculations, an adatom scheme we proposed for the basic 2 x 2, 4 x 4 and other structures. It was revealed that the 5 x 5 phase consisted of a linear chain of unevenly displaced, due to lattice relaxation, Ga adatoms along the [11•0] direction.

Structures of GaN(0001)-(2 x 2), -(4 x 4), and -(5 x 5) Surface Reconstructions. Q.K.Xue, Q.Z.Xue, R.Z.Bakhtizin, Y.Hasegawa, I.S.T.Tsong, T.Sakurai, T.Ohno: Physical Review Letters, 1999, 82[15], 3074-7