Aluminum nitride films on different orientations of sapphire and silicon

The details of epitaxial growth and microstrictural characteristics of AIN films grown on sapphire (0001), (<10(1)over bar 2>) and Si (100), (111) substrates were investigated using plan-view and cross-sectional high-resolution transmission electron microscopy and x-ray diffraction techniques. The films were grown by metalorganic chemical vapor deposition using TMA1+NH3N2 gas mixtures. Different degrees of epitaxy were observed for the films grown on alpha-Al2O3 and Si substrates in different orientations. The epitaxial relationship for (0001) sapphire was found to be (0001)(AIN)parallel to(0001)(sap) with in-plane orientation relationship of [<01(1)over bar 0>](AIN)parallel to[<(1)over bar 2><(1)over bar 0>](sap). This is equivalent to a 30 degrees rotation in the basal (0001) plane. For (<10(1)over bar 2>) sapphire substrates, the epitaxial relationship was determined to be (<11(2)over bar 0>)(AIN)parallel to(<10(1)over bar 2>)(sap) with the in-plane alignment of [001](AIN)parallel to[<(1)over bar 011>](sap). The AIN films on (0001) alpha-Al2O3 were found to contain inverted domain boundaries and a/3[<11(2)over bar 0>] threading dislocations with the estimated density of 10(10) cm(-2). The density of planar defects (stacking faults) found in AIN films was considerably higher in the case of (<10(1)over bar 2>) compared to (0001) substrates. Films on Si substrates were found to be highly textured c axis oriented when grown on (111) Si, and c axis textured with random in-plane orientation on (100) Si. The role of thin-film defects and interfaces on device fabrication is discussed. (C) 1996 American Institute of Physics.