Substrate Engineering with Fluoride Buffer Layers on Si

Abstract

ABSTRACTHere, we report on our efforts to engineer Si substrates for growth of compound semiconductors through the use of suitable epitaxial buffer layers of CaF2, SrF2, and BaF2 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 CaF2 and SrF2 grown directly on Si (111) and BaF2 grown directly on Si (001). The BaF2 is (111) oriented on the Si (001) substrates with one of the {110} planes of the BaF2 aligned with the (110) plane in the Si (001). PbS1−xSex of excellent epitaxial quality has recently been demonstrated on the BaF2 (111)/Si (001) films. Comparable epitaxial quality has been demonstrated for CaF2 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.