The effect of trace arsenic on the growth and surface structure of GaN(0 0
0 1) has been studied. We find that a partial pressure of only 10(-9) Torr
of arsenic during molecular beam epitaxial growth significantly modifies th
e growth kinetics. Such a small background pressure of arsenic leads to an
arsenic-terminated surface displaying a 2 x 2 reconstruction during growth
which is absent for the clean surface. First-principles theoretical calcula
tions show that As-terminated surfaces an energetically more favorable than
Ga-terminated surfaces for arsenic pressures of 10(-9) Torr, and structura
l models for the As-adatom 2 x 2 reconstruction are presented. (C) 2000 Els
evier Science B.V. All rights reserved.