Properties of ZnO(0001) layers grown by metalorganic chemical vapor deposition on GaN(0001) templates

摘要

We studied the properties of ZnO(0001) layers grown by metalorganic chemical vapor deposition on GaN(0001) templates. A two-step growth procedure was used where a buffer layer was first deposited at 400 °C before the temperature was increased to 900 °C for the deposition of the epitaxial layer. Atomic force microscopy revealed locally straight steps on a 20 × 20 μm~2 scan area. This indicates a step-flow growth mode. The root-mean-square roughness was 2.6 nm. The surface exhibited hexagonal pits. The pit density was 7.5 × 10~5-2.1 × 10~8 cm~(-2). The full width at half maximums of ω-scans for the sym-metric (0002) and the skew-symmetric (2021) reflections were 0.091° and 0.159°, respectively. The ZnO films were fully relaxed as revealed by reciprocal space maps for the (1015) reflection. Gallium doped n-type ZnO lay-ers were deposited on (In,Ga)N light emitting diodes as transparent contacts. The electron concentration was 9.4× 10~(19) cm~(-3) and the sheet resistance 45 Ω/sq. The resistivity and the mobility was 1.5 × 10~(-3) Ωcm and 43 cm~2/(Vs), respectively.