Studies on epitaxial relationship and interface structure of AlN/Si(111) and GaN/Si(111) heterostructures

We present the details of epitaxial growth interface structure of single wurtzite AlN thin films on (I 11) Si substrates by laser-molecular-beam-epitaxy. High quality AlN thin films with atomically sharp interfaces can be obtained by Laser-MBE at a substrate temperature of 650 +/-10degreesC. X-ray diffraction and high resolution transmission electron microscopy was used to study the details of epitaxial growth of AlN on Si(1 1 1) substrate. The orientation-relationship of AlN on Si(1 1 1) was studied from Si <1 1 0> and <1 1 2> zone axis and determined to be AlN [2 (1) over bar (1) over bar 0]parallel toSi[(1) over bar 1 0]and AlN[0 1 01(1) over bar 01 0]parallel toSi[(2) over bar 1 1]. The atomic structure of the interface was studied by high-resolution transmission electron microscopy and Fourier filtered image of cross-sectional AlN/Si(1 1 1) samples from both Si<1 1 0> and <1 1 2> zone axis. The results revealed the domain matching epitaxy of 4:5 ratio between the interplanar distances of Si(1 1 0) and AlN [2 (1) over bar (1) over bar 0]. We also present similarities and differences between the growth mechanism of AlN/Si(1 1 1) and GaN/Si(1 1 1) heterostructures.