MICROELEmONIC ENGINEERING ELSEVIER Microelectronic Engineering 25 (1994) 171-176 Charge transfer in p+-Si / Sil.,Ge, modulation doped heterostructures grown by RTCVD P. WARREN, I. SAGNES, D. DUTARTRE, and P.A. BADOZ FRANCE TELECOM-CNET, BP 98, F-38243 Meylan Cedex FRANCE J.M. BERROIR, Y. GULDNER, J.P. VIEREN, and M. VOOS Laboratoire de Physique de la Mat&e Condenste, Ecole Normale Superieure, 24 me Lhomond, F-75005 Paris, FRANCE High-quality Si/Sil_,Ge, simple (both normal and inverted) and double modulation doped heterostructures with 0~~~0.3 have been grown on Si(100) substrates by rapid thermal chemical vapor deposition (RTCVD) at low temperature (61O”C), using silane, germane and diborane in a hydrogen carrier gas. Hall measurements have been performed from 300 to 20 K and show the hole confinement in the Sir_,Ge, layer. The dependence of the confined density and hole mobility on germanium concentration and Si spacer thickness is presented. A simple calculation taking into account a single quantized energy level at each Si/SiGe interface has been made and yields confined densities in good agreement with experimental results. Magnetotransport measurements have been performed on several samples, and well defined Shubnikov de Haas oscillations and integral quantum Hall plateaus up to v=32 can be observed at 1.6 K in the magnetic field range 2-13 teslas. These data confirm the existence of a two dimensional hole gas at each Si/SiGe interface, with a density ranging from 3.1011 to 1012 cm-z, and a top mobility above 4000 cm2Ns, comparable to the best results obtained in similar MBE grown structures. Finally, these results demonstrate that high-quality p-type modulation- doped Si/Sil_,Ge, heterostructures can be grown by RTCVD at low temperature, and illustrate the latter’s capabilities in terms of doping abruptness and interface quality. INTRODUCTION The last few years have seen enormous advances in Si/Sir_,Ge, material systems. Rapid thermal chemical vapor deposition has emerged as a competing growth technology as it does not require ultra high vacuum technology like MBE or UHV-CVD, and permits growth temperatures and gas flows adapted to each epilayer. Devices based on Si/Sil_,Gex heterostructures require a good knowledge of the doping abruptness and interface quality. SIMS and RBS measurements, however, lack resolution on the nanometer scale. On the other hand, the transport properties of two dimensional hole gases (2DHGs) confined at a Si/Sil_,Ge, interface are very sensitive to the heterointerface region. Thus, in Si/Sil_,Gex, such modulation doped heterostructures have attracted considerable attention [l-7] in order to investigate not only the band structure, but also the doping profiles and interface quality. In this paper, we report the growth of simple (both normal (N) and inverted (I)) and double (D) modulation doped heterostructures. We present the study of charge transfer versus germanium content and spacer thickness by standard Hall measurements, Shubnikov de Haas (SdH) and quantum Hall effect (QHE) measurements. All these electrical measurements demonstrate: i) the equivalent 2D hole confinement of the two Si/SiGe and SiGe/Si interfaces in the Sir_xGex channel, and ii) the increase in confined density with increasing Ge content and decreasing spacer thickness. Elsevier Science B.V. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA SSDI 0167-9317(94)00014-L