MBE growth of PbSe/CaF2/Si(111) heterostructures

Successful epitaxial growth of PbSe/CaF2/Si(1 1 1) heterostructures using just one growth chamber of a molecular beam epitaxy system is described. Sharp (1 x 1) streaks in the RHEED pattern confirm the high structural quality of PbSe, and SEM and Nomarski microscopy reveal smooth PbSe surfaces. The PbSe epilayers show mobilities as high as 23 200 cm(2) V-1 s(-1) and electron concentrations of 1-2 x 10(17) cm(-3) at 77 R. In addition, observation of RHEED intensity oscillations confirm layer-by-layer growth modes for both CaF2 and PbSe. The PbSe/CaF2 interface has also been characterized by using X-ray photoelectron spectroscopy. All the Ca 2p, F 1s, Pb 4f and Se 3d peaks show chemical shifts as PbSe coverage on CaF2 increases. Results show that the PbSe/CaF2 interface consists of a thin transition layer dominated by Pb-F and Ca-Se bonds.