Unique properties of molecular beam epitaxy silicon on sapphire using in situ high-temperature substrate annealing compared with chemically vapor deposited silicon on sapphire

The dramatically different and superior properties of molecular beam epitaxy (MBE) of silicon on sapphire (SOS) have been investigated and compared with standard commercially available chemically vapor deposition (CVD) SOS. X-ray diffraction reveals a 24% reduction in the strain of the MBE SOS relative to the CVD SOS. The MBE SOS has a 40% higher electron Hall mobility at room temperature. At liquid N 2 temperatures, the electron Hall mobility of the MBE SOS increases instead of decreasing as in CVD SOS. The microtwin differential volume fraction profile for MBE SOS is lower by more than an order of magnitude compared with that of CVD SOS; it decreases faster with distance from the Si-sapphire interface; and it effectively goes to zero at 0.3 μm from the interface. The average Si-sapphire interface charge for MBE SOS is −8.0×10 10 cm −2 , which is negative and more than an order of magnitude lower than the interface charge of 2×10 12 cm −2 for CVD SOS. Some of the unique features of the Naval Research Laboratory VG80 Si MBE/Surface-Analytical System are discussed.