Characterization of Ge Doping on Sb2Te3 for High-Speed Phase Change Memory Application*Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDA09020402, the National Key Basic Research Program of China under Grant Nos 2013CBA01900, 2010CB934300, 2011CBA00607 and 2011CB932804, the National Integrate Circuit Research Program of China under Grant No 2009ZX02023-003, the National Natural Science Foundation of China under Grant Nos 61176122, 61106001, 61261160500 and 61376006, the Science and Technology Council of Shanghai under Grant Nos 12nm0503701, 12QA1403900, 13ZR1447200 and 13DZ2295700. (July 2015)