Molecular Beam Epitaxy Facility The MBE facility is based on a third-generation Model 930 system design from EPI and custom-designed processing chambers connected in-vacuo with the deposition system. The EPI 930, with cryo and ion pumping, full cryo-shrouds, and water-cooled thermal shields, achieves base pressures of about 8 10-11 torr and produces high quality GaAs, AlGaAs, and InGaAs layers in support of ongoing research at Brown. Wide bandgap III-nitride layers can be produced using rf or ECR plasma nitrogen sources. A 200-amu range quadrupole mass spectrometer, 10-kV RHEED gun, and 1-micron narrow-band optical pyrometer comprise the in-process diagnostic tools. MRSEC funds contributed to a novel in-situ optical monitoring technique available on the system. A multi-beam optical stress sensor (MOSS) is mounted on the center viewport of the source flange and provides real-time measurements of the wafer curvature due to stress generated by heteroepitaxial growth. The use of multiple parallel optical beams affords noise immunity so that a radius of curvature of 40 kilometers can be detected. The in-situ processing extension provides two ultrahigh vacuum chambers for sample preparation and etching, enabling regrowth of epitaxial layers on patterned substrates. The etching chamber offers ECR plasma, rf plasma, and thermal chlorine etch processes, using helium as a buffer gas. A second ultraclean chamber with an atomic hydrogen source is used for reducing native oxides and annealing etch-damaged surfaces. Samples can be transferred rapidly between the processing and growth chambers, enabling high-quality epitaxial regrowth on etched surfaces. The system was built by Prof. Beresford and is overseen by him. There is no formalized billing system for this instrument. Instead, projects are developed with collaborators, who share the costs of substrates, consumable items, and maintenance. The centers and programs that are major users of the facility cooperate to fund the personnel who run it. For further information contact:
Rod Beresford |
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Copyright © 2003, Center for Advanced Materials Research |