Electrical characterization of ultrathin atomic-layer-deposited Al/sub 2/O/sub 3/ on GaAs

Al₂O₃ is a widely used insulating material for gate dielectric, tunneling barrier and protection coating due to its excellent dielectric properties, strong adhesion to dissimilar materials, and its thermal and chemical stability. Al₂O₃ has a high bandgap (~9 eV), a high breakdown electric field (5-10 MV/cm), a high permittivity (8.6-10) and high thermal stability (up to at least 1000 degC) and remains amorphous under typical processing conditions. The Al₂O₃ samples in our experiments are grown on n-type GaAs substrate by atomic layer deposition (ALD). ALD is an ultra-thin-film deposition technique based on sequences of self-limiting surface reactions enabling thickness control on atomic scale. Compared with other conventional methods, such as sputtering, oxidation of aluminum films or chemical vapor deposition (CVD), ALD provides much higher quality in terms of low defect/trap density, high conformity and uniformity. The ultrathin Al₂O₃ films were grown in an ASM Pulsar2000TM ALD module with trimethylaluminum and water as the reactants at 300 degC after an appropriate surface cleaning process