Abstract
Self-running Ga droplets on GaAs (001) surfaces are repeatedly and reliably formed in a molecular beam epitaxial (MBE) chamber despite the lack of real-time imaging capability of a low-energy electron microscope (LEEM) which has so far dominated the syntheses and studies of the running droplets phenomenon. Key to repeatability is the observation and registration of an appropriate reference point upon which subsequent sublimation conditions are based. The reference point is established using reflection high-energy electron diffraction (RHEED), not the noncongruent temperature used in LEEM where temperature discrepancies up to 25°C against MBE is measured. Our approach removes instrumental barriers to the observation and control of this complex dynamical system and may extend the usefulness of many droplet-related processes.
Highlights
Droplets on semiconductor surfaces play important roles in various devices and processes
We report a simple procedure that leads to a reliable formation of self-running Ga droplets on GaAs (001) using in situ reflection high-energy electron diffraction (RHEED) patterns as the primary reference
For every significant change in the RHEED pattern, the heating is stopped, the sample is removed, and the surface morphology is studied by two microscopic techniques: optical microscopy (OM) with differential interference contrast (DIC) enhancement (Nikon’s Eclipse ME600P, Tokyo, Japan), and atomic force microscopy (AFM) using silicon nitride tips in the tapping mode in air (Seiko’s SPA400, Seiko Instruments, Tokyo, Japan)
Summary
Droplets on semiconductor surfaces play important roles in various devices and processes. A pioneering experiment involving Ga droplet dynamics on GaAs (001) was reported [9], stimulating further investigations in related systems [10,11,12,13]. These reports are conducted principally by in situ real-time observation under a low-energy electron microscope (LEEM), with limited availability, leading some to experiment using more readily available molecular beam epitaxial (MBE) chambers [14,15,16], albeit with limited yields since MBE is optimized for deposition, not for microscopy. It is accepted that group III droplets nucleate and run on certain III-V surfaces undergoing
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