ZNO FILMS DEPOSITED ON GAAS SUBSTRATES WITH A SIO2 THIN BUFFER LAYER

Sputter deposition of ZnO films on GaAs substrates has been investigated. ZnO films were radio frequency (rf)-magnetron sputter deposited on GaAs substrates with or without SiO2 thin buffer layers. Deposition parameters such as rf power, substrate-target distance, and gas composition/pressure were optimized to obtain highly c-axis oriented and highly resistive films. Deposited films were characterized by x-ray diffraction, scanning electron microscopy (SEM), capacitance, and resistivity measurements. Thermal stability of sputter-deposited ZnO films (0.5-2.0 mum thick) was tested with a post-deposition heat treatment at 430-degrees-C for 10 min, which is similar to a standard ohmic contact alloying condition for GaAs. The ZnO/SiO2/Ga-As films tolerated the heat treatment well while the ZnO/GaAs films disintegrated. The resistivity (10(11) OMEGA-cm) of the ZnO films on SiO2-buffered GaAs substrates remained high during the heat treatment. The post-deposition anneal treatment also enhances c-axis orientation of the ZnO films dramatically and relieves intrinsic stress almost completely. These improvements are attributed to a reduction of grain boundaries and voids with the anneal treatment as supported by SEM and x-ray diffraction measurement results.