EFFECT OF ILLUMINATION ON TRANSPORT-PROPERTIES OF THE HIGH-MOBILITY 2D HOLE GAS IN SI-SIGE HETEROSTRUCTURES

The effect of illumination on transport properties of the two-dimensio nal hole gas (2DHG) in Si-SiGe heterostructures is found to irreversib ly alter its 2D transport properties, analogous to the persistent phot oconductivity effect in GaAs-based devices. The relatively small chang e of the 2D hole concentration from 3.75 x 10(11) cm(-2) before illumi nation to 4.23 x 10(11) cm(-2) after illumination is accompanied by a significant increase in the in-plane effective mass from (0.23-0.25)m( e) to (0.32-0.33)m(e), and an even larger increase in the quantum life time. To evaluate the g-factor of this highly spin degenerate 2DHG we use highly sensitive magneto photoconductivity measurements to obtain g = 9.1 +/- 0.1 after illumination, compared to an estimate for dark state g = 8.5 +/- 0.5. (C) 1998 Published by Elsevier Science B.V. Al l rights reserved.