We have investigated the optical and transport properties of MBE grown
short-period superlattices of InAs/GaAs with different numbers of periods (3 <=
N <= 24) and a total thickness 14 nm. Bandstructure calculations show that
these superlattices represent a quantum well with average composition
In_0.16Ga_0.84As. The electron wave functions are only slightly modulated by
the superlattice potential as compared to a single quantum well with the same
composition, which was grown as a reference sample. The photoluminescence, the
resistance, the Shubnikov-de Haas effect and the Hall effect have been measured
as a function of the InAs layer thickness Q in the range 0.33 <= Q <= 2.7
monolayers (ML). The electron densities range from 6.8 to 11.5x10^11 cm^-2 for
Q <= 2.0 ML. The photoluminescence and magnetotransport data show that only one
subband is occupied. When Q >= 2.7 ML quantum dots are formed and the metallic
type of conductivity changes to variable range hopping conductivity.Comment: 15 pages (incl.7 figures); pdf file; submitted to Semicond. Sci.
Techno
