Issues on the molecular-beam epitaxial growth of p-SiGe inverted-modulation-doped structures

The influence of boron segregation and silicon cap-layer thickness on two-d imensional hole gases (2-DHGs) has been investigated in Si/Si0.8Ge0.2/Si in verted-modulation-doped heterostructures grown by solid-source molecular-be am epitaxy. Boron segregation, which is significant in structures with smal l spacer layers, can be suppressed by growth interruption after the boron d oping. How growth interruption affected the electrical properties of the 2- DHG and the boron doping profile as measured by secondary ion mass spectros copy are reported. We report also on the role played by the unpassivated si licon cap, and compare carrier transport at the normal and inverted interfa ces. (C) 1999 American Institute of Physics. [S0003-6951(99)04204-7].