Formation of high-quality oxide/Ge1−xSnx interface with high surface Sn content by controlling Sn migration

摘要

In this paper, we investigated how Sn migrated during annealing for Ge1−xSnx at its surface and in its interior, as well as the Ge oxide formation on Ge1−xSnx with controlling surface oxidation. After oxidation at 400 °C, X-ray photoelectron spectroscopy and X-ray diffraction measurements revealed Sn migration from inside the epitaxial Ge1−xSnx layer to its surface. Annealing was not the primary cause of significant Sn migration; rather, it was caused mostly by oxidation near the Ge1−xSnx surface. This process formed a Ge1−xSnx 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 GeO2 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 Ge1−xSnx gate stack.