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

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.