Effects of Low-Temperature GeSn Buffer Layers on Sn Surface Segregation During GeSn Epitaxial Growth

Abstract

We investigate the effects of the low-temperature (LT) GeSn buffer layers on Sn surface segregation during the growth of the additional GeSn layers. Sn surface segregation was observed in the GeSn layers formed on Si substrates at the growth temperature of 300 °C. However, there was no Sn surface segregation in the GeSn layers grown at 300 °C on the LT GeSn buffer layers formed at 225 °C. The Sn surface segregation was limited by the effects of the LT buffer layers. Crystallinity of the GeSn layers grown at 300 °C on the LT GeSn buffer layers was investigated by Raman spectroscopy. The full width at half maximum of the Ge–Ge Raman spectrum obtained from the GeSn layers was about 3.1 cm−1, which means that the formed GeSn layers have excellent crystallinity. We have successfully demonstrated that the LT GeSn buffer layers can limit the Sn surface segregation, which increases the growth temperature and improves crystallinity of the GeSn layers.