AVS 57th International Symposium & Exhibition
    Energy Frontiers Topical Conference Thursday Sessions
       Session EN+AS-ThM

Paper EN+AS-ThM4
Characterization of Minority Carrier Lifetime in Ge Films Epitaxially Grown on Si by Nanoscale Interfacial Engineering

Thursday, October 21, 2010, 9:00 am, Room Pecos

Session: Surface and Interface Analysis of Materials for Energy
Presenter: J.J. Sheng, University of New Mexico
Authors: J.J. Sheng, University of New Mexico
D. Leonhardt, University of New Mexico
J.G. Cederberg, Sandia National Laboratories
M.S. Carroll, Sandia National Laboratories
M.J. Romero, National Renewable Energy Laboratory
S. Johnston, National Renewable Energy Laboratory
S.M. Han, University of New Mexico
Correspondent: Click to Email
High-quality Ge-on-Si (GoS) heterostructures are pursued for many applications, including near infrared (NIR) photodetectors and integration with III-V films for multijunction photovoltaics. However, such integration poses many engineering challenges, ranging from lattice mismatch, to thermal expansion coefficient mismatch, to non-planar morphological evolution. We have previously demonstrated a scale-up of growing low-dislocation-density Ge on Si by manipulating the Ge-Si interface at the nanoscale, using a thin chemical SiO2 layer and a surface reaction involving Ge and SiO2. We have also developed a slurry-free, chemical-mechanical polish step to planarize the GoS surface resulting in a Ge surface with a root mean square (RMS) roughness of less than 1 nm. Herein, we focus on the characterization of carrier lifetime in the Ge epilayers grown on Si by the said nanoscale Ge-Si interfacial engineering. Using photoconductivity decay techniques, minority carrier lifetime is measured in the GoS substrates to extract surface recombination velocity as well as carrier lifetime in bulk Ge. The effective surface recombination velocity, representing both Ge-Si interface decorated with chemical SiO2 and Ge surface, is approximately 1.26x104 cm/sec, largely dominated by recombinations at the oxide. We observe that the extracted lifetimes, which vary with the Ge film thickness, correlate well with the dislocation density that varies as a function of distance from the Ge-Si interface. In this presentation, we will further discuss capacitance-voltage characterization of metal-oxide-semiconductor structures fabricated on our GoS substrates.