Amorphous semiconductor superlattice is attractive for developing new electronic devices. The superlattice structure with a-Si: H and a-AIO has a deep quantum well of a-Si: H, since a-AIO has a larger bandgap and a smaller electron affinity as compared with those of a-Si: H. Photo-CVD with ArF excimer laser (λ=193nm) makes use of photolysis of the source gases and is suitable for the superlattice formation because of little interface damage.
We form a-Si: H/a-AIO superlattice and investigate its electrical and optical properties. Deposition of a-Si: H layer and a-AlO was performed with Si₂H₆ gas, and TMA (trimethylaluminium) and oxygen gas on quartz or silicon substrates heated at 200°C and 300°C, respectively.
Si, O and Al signals increase and decrease periodically on the depth profiles by Auger electron spectroscopy analysis, showing the periodical change of the composite elements. Optical bandgap was detemined from wave length dependence of absorption coefficient (Tauc plot). The optical bandgap increases with the decrease of the well-layer thickness of the superlattice, which is due to the quantum level formed in the quantum well. Photo- and dark-conductivity of superlattice paralell to the layers increase as compared with that of monolayer a-Si: H. This result is an inherent characteristics of superlattice.