M-plane III-nitride materials for polarization sensitive devices grown by PAMBE with real time analysis by spectroscopic ellipsometry

摘要

In this paper we present a study of the growth of M-plane GaN epi layers on LiA1O_2 substrates under Ga rich conditions and growth at Ga stable conditions by plasma assisted molecular beam epitaxy (PAMBE) coupled with in-situ spectroscopic ellipsometry (SE). Previous studies on M-plane materials have suggested that optimum growth conditions with respect to surface morphology are those giving rise to Ga trilayer coverage at low growth temperature. By studying Ga dsorption/desorption in vacuum and in the presence of active nitrogen, we find that the total coverage for M-plane material is distinctly different for these two conditions. Under vacuum, the stable Ga coverage corresponded of 0.48 nm, while a thicker Ga stable coverage of 0.7 nm was determined N plasma. Using these GaN growth conditions, M-plane InGaN layers were grown and fabricated into polarization-sensitive photodetectors.