High quality heteroepitaxial AlN films on diamond

Heteroepitaxial AlN films grown on (100)- and (111)-oriented diamond (C-alpha) substrates by plasma-induced molecular beam epitaxy have been investigated by x-ray diffraction (XRD) and atomic force microscopy (AFM). High quality epitaxial growth of almost strain-free wurtzite AlN is observed for both orientations. For the AlN/C-alpha(111) heterostructures, the epitaxial orientation relationship (0001)[10 (1) over bar0] AlNparallel to(111)[01 (1) over bar] C-alpha is obtained. However, a significant fraction of up to 20% of the epitaxial layer is oriented differently with (10 (1) over bar1) AlNparallel to(111) C-alpha. In case of AlN on C-alpha(100), a double-domain structure with either (0001)[10 (1) over bar0] AlN(I)parallel to(100)[011] C-alpha or (0001)[(`) over bar2 (1) over bar0] AlN(II)parallel to(100)[011] C-alpha is found. The linewidths of the XRD omega and 2theta/omega scans of the symmetric AlN 002 reflection have been determined as 1.4 and 0.17degrees for AlN/C-alpha(100), 0.55degrees and 0.11degrees for AlN/C-alpha(111), as well as 0.51 and 0.05degrees for an AlN/sapphire (0001) reference sample grown under similar conditions. Thus, the crystal quality of AlN on C-alpha(111) is close to that of AlN on sapphire. The corresponding AlN rms roughness values found by AFM are 1.9 nm on C-alpha(100), 1.7 nm on C-alpha(111), and 3.2 nm on sapphire (0001), respectively. (C) 2004 American Institute of Physics.