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-dimensional hole gas (2DHG) in Si-SiGe heterostructures is found to irreversibly alter its 2D transport properties, analogous to the persistent photoconductivity effect in GaAs-based devices. The relatively small change of the 2D hole concentration from 3.75 x 10(11) cm(-2) before illumination 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 lifetime. 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. All rights reserved.