Properties of MOVPE GaN grown on ZnO deposited on Si(0 0 1) and Si(1 1 1) substrates

Abstract

GaN/ZnO layers were grown on p-type Si(0 0 1) and Si(1 1 1) substrates to develop preparation techniques of multi-material devices for optoelectronic and sensor applications. At the first stage the thin, polycrystalline, zinc oxide (ZnO) buffer layers were deposited on p-type Si substrates by radio frequency (RF) sputtering techniques. The planar RF sputtering Perkin Elmer 2400/8L diode system equipped with hot-pressed ceramic ZnOAl target (99.99%purity) was employed. The sputtering power was 300 and 150 W, accordingly thicknesses of ZnO:Al films were 280 and 250 nm. At the next stage the GaN layers were grown on ZnO/Si substrates in an atmospheric pressure, single wafer, horizontal flow metalorganic vapor phase epitaxy (MOVPE) system. The low frequency (40 kHz) inductive heating method was used to raise the temperature of graphite susceptor up to 1030 °C. Trimethylgallium (TMGa), trimethylaluminium (TMAl) and ammonia (NH 3) were used with H 2 carrier gas. The new type of temperature graded nitride multi-layers (NMLs) were applied and the multi-stage growth process was developed to prevent the ZnO layer decomposition during exposure to NH 3 and H 2 at high temperature. Atomic force microscopy (AFM) and X-ray diffractometry (XRD) were applied to study the morphology and structural properties of the ZnO and GaN layers. The experimental conditions were selected for successful integration of high temperature gallium nitride (HT-GaN) layers with the ZnO films on Si substrate.