Ge epitaxial layer is grown on a bonded Si-on-quartz (SOQ) wafer by ultrahigh vacuum chemical vapor deposition. A tensile strain as large as 0.4% is generated in Ge grown on SOQ, which is almost two times larger than ~0.2% in Ge grown on an ordinary Si-on-insulator (SOI) wafer. The enhancement of tensile strain is derived from an increased thermal expansion mismatch between the Ge layer and the base substrate of quartz in SOQ, whose thermal expansion coefficient of 0.5 × 10-6 K-1 is smaller than 2.6 × 10-6 K-1 for Si base substrate in SOI. Because of the strain-induced bandgap narrowing, the direct bandgap energy is reduced from ~0.77 eV for Ge on SOI to ~0.75 eV for Ge on SOQ. Performances are discussed when the strain-enhanced Ge layer on SOQ is applied to near-infrared photonic devices of photodetectors and light emitters.
A spontaneous formation of SiGe is reported, which is induced at mesa sidewalls of Si-capped Ge epitaxial layers selectively grown on Si. Ultrahigh-vacuum chemical vapor deposition is used to grow Ge mesa stripes on (001) Si wafers partially covered with SiO2 masks, followed by a growth of Si capping layer. Micro-Raman spectra reveals that SiGe is formed selectively on the {113} sidewalls of Ge mesa structure running in the [110] direction, resulting from an intermixing between the Si capping and Ge layers, whereas no such SiGe is detected on the flat-top (001) mesa surface. An increased amount of SiGe is observed for stripe patterns misaligned from the [110] direction. This suggests that the atomic step/roughness on the sidewall contributes to the intermixing. The observed SiGe formation would be applied to the bandgap engineering to tune the operation wavelengths in Ge photonic devices on Si. In fact, a significant blue shift in the direct-gap light emission peak is observed for submicron-wide Ge mesa structures with no flat-top (001) surface, where the surface is totally surrounded by SiGe.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.