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Growth of Epitaxial Germanium Thin Films at Low Temperature by Reactive Thermal Chemical Vapor Deposition
K. Tao, J. Wang, W. Zhang, Y. Kurosawa, J.-I. Hanna
Germanium, Epitaxial Growth, Reactive Thermal Chemical Vapor Deposition, Threading Dislocation Density
Material Studies, New Concepts and Ultra-High Efficiency
Subtopic: New Materials, Cells and Modules
Event: 27th European Photovoltaic Solar Energy Conference and Exhibition
Session: 1BV.7.21
314 - 317
ISBN: 3-936338-28-0
Paper DOI: 10.4229/27thEUPVSEC2012-1BV.7.21
0,00 EUR
Document(s): paper


The authors report the epitaxial growth of germanium (epi-Ge) thin films on Si(100) substrate at low substrate temperature of 350oC using reactive thermal chemical vapor deposition. Si2H6 and GeF4 are used as source gases. The influences of gas pressure and gas flow ratio of Si2H6/GeF4 on the properties of epi-Ge are investigated. The results indicate that low pressure leads to Stranski-Krastanov growth mode in which pyramidal structures develop on the surface of epi-Ge film, and, the size of pyramids as well as the surface RMS roughness can be reduced by increasing the gas pressure. Both the content of Ge and the crystallinity of the epitaxial films can be enhanced by increasing gas pressure and/or decreasing gas flow ratio of Si2H6/GeF4. The RMS roughness of epi-Ge films can be decreased largely when the gas flow ratio is lower than 3.0. The change of surface morphology is proved to be correlated with the reaction between GeF4 and the growth surface of films. By increasing gas pressure to 8.0torr and decreasing the gas flow ratio to 2.0, for 1.21μm-thick epi-Ge films, a threading dislocation density of ~7.0×105cm-2 is achieved, along with a surface RMS roughness of ~2.0nm.