Dislocations in P-MBE Grown ZnO Layers Characterized by HRXRD and TEM

Abstract

We have characterized dislocations in ZnO layers grown on c‐sapphire (α‐Al2O3) by plasma‐assisted molecular‐beam epitaxy (P‐MBE) with and without MgO buffer layer. ZnO without MgO buffer was grown three‐dimensionally (3D), while ZnO with MgO buffer was grown two‐dimensionally (2D). Mosaic spread (tilt and twist angles), types and density of dislocations in the layers were studied by both high‐resolution X‐ray diffraction (HRXRD) and transmission electron microscopy (TEM). HRXRD experiments reveal that screw dislocation densities in the ZnO layer are 8.1×108 cm−2 and 6.1×105 cm−2, for ZnO with and without MgO buffer, respectively, while edge dislocation densities are 1.1×1010 cm−2 and 1.3×105 cm−2, for ZnO with and without MgO buffer, respectively. HRXRD and TEM data showed the same result that the major dislocations in the ZnO layers are edge type dislocations running along c‐axis. Therefore, HRXRD technique can be applied to characterize dislocations in ZnO layers.