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Advances in Condensed Matter Physics
Volume 2015 (2015), Article ID 785415, 9 pages
Research Article

High-Electron-Mobility SiGe on Sapphire Substrate for Fast Chipsets

1National Institute of Aerospace (NIA), 100 Exploration Way, Hampton, VA 23666, USA
2KAIST Research Analysis Center (KARA), Korea Advanced Institute of Science and Technology (KAIST), Science Road, Yuseong-Gu, Daejeon 305-701, Republic of Korea
3NASA Langley Research Center, Hampton, VA 23681-2199, USA

Received 1 September 2014; Revised 28 November 2014; Accepted 29 November 2014

Academic Editor: Yi Zhao

Copyright © 2015 Hyun Jung Kim et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


High-quality strain-relaxed SiGe films with a low twin defect density, high electron mobility, and smooth surface are critical for device fabrication to achieve designed performance. The mobilities of SiGe can be a few times higher than those of silicon due to the content of high carrier mobilities of germanium (p-type Si: 430 cm2/V·s, p-type Ge: 2200 cm2/V·s, n-type Si: 1300 cm2/V·s, and n-type Ge: 3000 cm2/V·s at 1016 per cm3 doping density). Therefore, radio frequency devices which are made with rhombohedral SiGe on -plane sapphire can potentially run a few times faster than RF devices on SOS wafers. NASA Langley has successfully grown highly ordered single crystal rhombohedral epitaxy using an atomic alignment of the direction of cubic SiGe on top of the direction of the sapphire basal plane. Several samples of rhombohedrally grown SiGe on -plane sapphire show high percentage of a single crystalline over 95% to 99.5%. The electron mobilities of the tested samples are between those of single crystals Si and Ge. The measured electron mobility of 95% single crystal SiGe was 1538 cm2/V·s which is between 350 cm2/V·s (Si) and 1550 cm2/V·s (Ge) at 6 × 1017/cm3 doping concentration.