EE PhD Oral Examination - Raja Jain (Monday, March 7, 2pm, Clark Center Auditorium)

Raja Jain jrjain at
Tue Mar 1 09:31:23 PST 2011

Tensile-Strained Germanium-on-Insulator for 

High-Performance Silicon-Compatible Optoelectronics



J. Raja Jain



PhD Dissertation Defense

Department of Electrical Engineering

Advisor: Prof. Roger T. Howe

Co-Advisor: Prof. Thomas M. Baer






Optoelectronics technology is increasingly pervasive and can be found in
systems ranging from portable devices to large-scale communications
installations. Most commercial devices use III-V materials to achieve high
performance; however, these materials have the disadvantages of high cost,
process complexity, and incompatibility with silicon (Si) CMOS
manufacturing. Germanium (Ge) has been demonstrated to be a promising
material in the effort to develop Si-compatible optoelectronics; however,
bulk Ge is unable to provide the performance necessary for adoption. In this
talk, we will discuss a new MEMS-based technology to improve the performance
of Ge optoelectronic devices.

The Ge-on-insulator (GOI) material system represents an attractive platform
for Si-compatible optoelectronics. Additionally, it is well-known that
applying tensile strain to Ge modifies its band structure to yield improved
light absorption and emission. We will introduce a Si-compatible platform
technology that borrows methods from the MEMS field to apply very large,
tunable tensile strains to suspended GOI films. We first show low defect
density, tensile-strained GOI substrates obtained using Ge-on-Si
heteroepitaxy and layer transfer techniques. We then present results from
enhanced photodetectors built on this platform, exhibiting large shifts of
the Ge direct bandgap that enable photodetection far beyond the L-band
wavelength range. Finally, we discuss results on light emission from the
tensile-strained GOI films, which demonstrate significant enhancement
compared to bulk Ge.

Ge-based solutions offer a promising route in terms of cost and integration
of optics and electronics. The tensile-strained GOI platform technology to
be discussed in this talk could enable manufacturable, high-performance
Si-compatible devices and represents a significant advancement in
optoelectronics technology.


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