Oxygen-doped Si epitaxial film (OXSEF)

We propose a new wide-gap material, an oxygen-doped Si epitaxial film (OXSEF), for applications to Si heterobipolar transistors (HBTs). OXSEF containing several tens of at.% of oxygen can be grown on a Si substrate by depositing Si in about 10 -6 Torr O 2 . OXSEF is literally almost a single crystal with an identical crystalline structure to Si, although it includes {111} twins as defects caused by oxygen. Temperature and O 2 pressure dependences of oxygen concentration in OXSEF are dominated by oxygen adsorption on the Si surface. Oxygen atoms in OXSEF segregate to some extent toform incomplete oxides like SiO 1.5 , but complete phase separation as a mixture of Si and SiO 2 . regions does not occur, probably bcause of non-equilibrium conditions in MBE growth. Valence band discontinuity at the Si/OXSEF interface is deduced to be 0.26 eV based on photoelectrical measurements.