This innovative facility is based on a 3rd-generation Model 930 system design from EPI and custom-designed processing chambers connected in vacuo with the deposition system. It is directed by Beresford. 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 III-V arsenide and nitride layers. The system includes a valved As cracker that permits precise mechanical control of the As2 or As4 flux and dual-filament Ga and In cells, whose "hot lip" design helps minimize defect densities in the films. A 200-amu range quadrupole mass spectrometer, 10-kV RHEED gun and 1-µm narrow-band optical pyrometer are in-process diagnostic tools. Upgrades include customized ECR and rf plasma nitrogen sources. A novel multi-beam optical stress sensor (MOSS) mounts 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 substrates can be loaded in stress-free mounts such that they are free to deform when mismatched epitaxial layers are grown. The use of multiple parallel optical beams affords noise immunity such that a radius of curvature of 40 km can be detected, sufficient for detection of monolayer films. An atomic hydrogen source enables low-temperature oxide desorption cleaning, which is critical for preparing engineered nanoscale surfaces for the pattern-driven growth of quantum structures. The average cost of 1 day of operations is ~$120 (excluding any personnel or substrate costs), covering liquid nitrogen, source materials, miscellaneous lab supplies, and routine costs of maintenance/repair of the MBE components and system.
No instruments are listed in this facility