Valence band discontinuity, surface reconstruction, and chemistry of (0001), (000(1)over-bar), and (1(1)over-bar-00) 2H-AlN/6H-SiC interfaces

A detailed examination of the valence band discontinuity (Delta E-upsilon) formed at the (0001), (<000(1)over bar>), and (<1(1)over bar>00) interfaces between 2H-AlN and 6H-SiC has been conducted using x-ray and UV photoelect ron spectroscopies. The Delta E-upsilon was observed to range from 0.6-2.0 eV depending on the growth direction (i.e., AlN on SiC vs SiC on AlN), as w ell as the crystallographic orientation, cut of the SiC substrate (i.e., on versus off axis), and SiC surface reconstruction and stoichiometry. A Delt a E-upsilon of 1.4-1.5 eV was observed for AlN grown on (3 x 3) (0001)(Si)6 H-SiC on-axis substrates; a Delta E-upsilon of 0.9-1.0 eV was observed for off-axis substrates with the same surface reconstruction. The values of Del ta E-upsilon for AlN grown on (root 3 x root 3)R30 degrees(0001) 6H-SiC on- and-off-axis substrates were 1.1-1.2 eV. A larger valence band discontinuit y of 1.9-2.0 eV was determined for 3C-SiC grown on (0001) 2H-AlN. Smaller v alues of Delta E-upsilon of 0.6-0.7 and 0.8-0.9 eV were observed for AlN gr own on on-axis (<000(1)over bar>)(C) and (<1(1)over bar>00)6H-SiC substrate s, respectively. (C) 1999 American Institute of Physics. [S0021-8979(99)010 20-8].