Si/SiGe valence band offset determination using photoluminescence and DLTS in SiGe quantum-well MOS capacitors

Optical and electrical characterization is carried out on MOS capacitor structures including buried strained Si1-xGex quantum-wells to determine the channel and hetero-interface parameters. Well resolved SiGe band-gap edge Photoluminescence (PL) is observed for all the samples. The energy locations are in agreement with the announced Ge contents and quantum-well thickness. The presence of dislocations is not detected, indicating a good Si/SiGe interface structural quality. The results show that the hole concentration in the quantum-well is a function of the pulse duration (t(p)) of the excitation signal used for the DLTS spectroscopy. Using the DLTS, the valence-band offset (Delta E-v) is determined for various Ge contents up to 35%. This work points out that the coupling of the optical (PL) and electrical (C-V and DLTS) characterization provides a consistent tool for the analysis of Si/SiGe heterostructure based devices. (C) 1998 Elsevier Science B.V. All rights reserved.