No abstract

Here, we report on our efforts to engineer Si substrates for growth of compound semiconductors through the use of suitable epitaxial buffer layers of CaF 2 , SrF 2 , and BaF 2 using a recently installed dual growth chamber MBE system. We have also developed new graphite-heater K-cells which have demonstrated reliable, high temperature deposition of the fluorides with excellent uniformity across substrates up to 6 inches in diameter. Excellent epitaxial quality(xmin< 5.0%) and smooth surface morphologies have been achieved for epitaxial CaF 2 and SrF 2 grown directly on Si(lll) and BaF 2 grown directly on Si(001). The BaF 2 is (111) oriented on the Si(001) substrates with one of the {1TO} planes of the BaF 2 aligned with the (1TO) plane in the Si(001). PbS 1 _5Se 0 of excellent epitaxial quality has recently been demonstrated on the BaF 2 (111)/Si(001) films. Comparable epitaxial quality has been demonstrated for'CaF 2 grown on Si(001) substrates using a two step growth method. We also report on preliminary results on epitaxial mixed fluoride growth on Si(111) and Si (001) substrates.

A 3-dimensional phase diagram is introduced to describe the dependence of the RHEED pattern from GaAs(111)B surface on growth conditions. The 2×2, transitional(1×1), and √19×,√19 surface reconstructions correspond to different zones in the phase diagram. A equation is given for the planes that separate these zones, which fit experimental data well. Homoepitaxial films on GaAs(111)B grown in the 2×2 region generally have bad crystal quality as determined by the ion channeling, and growth in the √19×√19 region generally yields rough surface morphology. At higher substrate temperatures (∼ 650 °C), featureless films with minimum ion channeling yields of less than 4% are achieved.