Comparison of Charge Storage Behavior of Electrons and Holes in a Continuous Ge Nanocrystal Layer

The charge storages behaviors of electrons and holes injected into a continuous nc-Ge layer embedded in SiO₂ synthesized by the Ge ion implantation technique are investigated. The hole injection is found to exhibit a much higher charging speed as well as a better retention in the nc-Ge layer as compared to the electron injection. The better hole retention is explained in terms of slower charge loss to the Si substrate as well as slower lateral charge diffusion as a result of the larger oxide barrier height. The faster hole injection is also attributed to the less significant lateral diffusion of injected holes during the charging period. The results indicate that the oxide barrier height plays an important role in the charge storage behaviors of electrons and holes injected into the continuous nc-Ge layer.