M-plane GaN(1(1)over-bar-00) grown on gamma-LiAlO2(100): nitride semiconductors free of internal electrostatic fields

We investigate the growth of wurtzite GaN along the non-polar [1 (1) over b ar 0 0] direction on gamma -LiAlO2(1 0 0) by plasma-assisted molecular beam epitaxy. The morphological and structural properties of buffer layers and their orientation-relationship to the substrate are examined by means of re flection high-energy electron diffraction, atomic force microscopy, X-ray d iffraction and Raman scattering. The layers are shown to be single-phase Ga N(1 (1) over bar 0 0) within the measurements' sensitivity. In contrast to the ubiquitous C-plane GaN[0 0 0 1] orientation, M-plane wurtzite nitrides are expected to be free of electrical polarization along the growth directi on. This is experimentally verified by the absence of internal electrostati c fields in (Al,Ga)N/GaN quantum wells as evidenced by continuous-wave and time-resolved luminescence. (C) 2001 Elsevier Science B.V. All rights reser ved.