Band offsetasymmetry and optical anisotropy in semiconductor heterostructures with no-common atom

摘要

In no-common atom systems (Ml-M2 chemical ClAl-C2A2), the interfaces involve chemical bonds which differ at the M1-M2 and M2-M1 interfaces, and differ from the chemical bonds in either material. As a conseuqnce the interface dipole contributions to the band offset are not the same: band offsets are not commutative. Experimental investigations in the (InGa)As-InP and InP-(AlIn)As show that "direct" and "inverse" interface offsets actually differ by as much as 70-100 meV. In addition, at a M1-M2 interface, all the Cl-Al bonds lie in the {110} plane while all the Al-C2 bonds are in the perpendicular {-110} plane. This local asymmetry allows some optical anisotropy around the growth axis. Polarization-resolved optical transmission measurements in both systems actually exhibilt a considerable optical anisotropy in the near band-gap spectral region. A k.p theory of these polarization anisotropy effects is briefly discussed.