SHALLOW ACCEPTORS IN STRAINED MULTI-QUANTUM-WELL GE GE1-XSIX HETEROSTRUCTURES/

Far infrared photoconductivity spectra due to excitation of shallow ac ceptors in strained multiquantum well Ge/Ge1-xSix (x approximate to 0. 1) heterostuctures are investigated. It is shown that these spectra ar e shifted toward longer wavelengths in the far infrared region compare d with those of bulk p-Ge, owing to ''built-in'' strain and size quant ization, which lead to splitting of the light- and heavy-hole subbands in the Ge layers. Shallow acceptor spectra are calculated variational ly for bulk germanium under uniaxial tension, which is ''equivalent'' to the strained Ge layers in the heterostructures. Although this metho d is only appropriate for wide quantum wells (d(Ge) approximate to 800 Angstrom), the calculations are shown to qualitatively account for ph otoconductivity spectra obtained from narrower wells (d(Ge) approximat e to 200 Angstrom) as well. (C) 1998 American Institute of Physics. [S 1063-7826(98)02010-9].