High Mobility SiGe/Si Transistor Structures on Sapphire Substrates Using Ion Implantation

High mobility n-type SiGe/Si transistor structures have been fabricated on sapphire substrates by ion implanting phosphorus ions into strained 100 for the first time. The strained Si channels were sandwiched between Sio.7Geo.3 layers, which, in turn, were deposited on Sio.7Geo.3 virtual substrates and graded SiGe buffer layers. After the molecular beam epitaxy (MBE) film growth process was completed, ion thick silicon channels implantation and post-annealing were used to introduce donors. The phosphorous ions were preferentially located in the Si channel at a peak concentration of approximately 1x1 O’* ~ r n ~ . Room temperature electron mobilities exceeding 750 cm2/V-sec at carrier densities of 1 ~ 1 0 ’ ~ cm-2 were measured. Electron concentration appears to be the key factor that determines mobility, with the highest mobility observed for electron densities in the 1 2 ~ 1 0 ’ ~ cm-2 range.