Formation of high-quality oxide/Ge_(1-x)Sn_x interface with high surface Sn content by controlling Sn migration

摘要

In this paper, we investigated how Sn migrated during annealing for Ge_(1-x)Sn_x at its surface and in its interior, as well as the Ge oxide formation on Ge_(1-x)Sn_x with controlling surface oxidation. After oxidation at 400 ℃, X-ray photoelectron spectroscopy and X-ray diffraction measurements revealed Sn migration from inside the epitaxial Ge_(1-x)Sn_x layer to its surface. Annealing was not the primary cause of significant Sn migration; rather, it was caused mostly by oxidation near the Ge_(1-x)Sn_x surface. This process formed a Ge_(1-x)Sn_x oxide with a very high Sn content of 30%, inducing a wide hysteresis loop in the capacitance-voltage characteristics of its corresponding MOS device. We also found that forming a thin GeO_2 layer by using a deposition method that controls Ge surface oxidation produced low densities of interface states and slow states. From these results, we conclude that controlling Sn migration is critical to forming a high-quality Ge_(1-x)Sn_x gate stack.