Laser Atomic Cleaning And Initial Stages Of Epitaxial Growth Of Germanium Films On (100) Silicon During Laser Physical Vapor Deposition

Abstract

Thin films of epitaxial germanium were deposited on (100) silicon substrates which were atomically cleaned using a pulsed excimer laser ( wavelength 308 nm, pulse duration 45 nanosecond, and energy density (0.75 - 1 J cm-2 ) in high vacuum ( 3.0 x 10-7 torr ). Thin films of germanium were then deposited in similar vacuum using the excimer laser at a higher energy density (3.5-6 J cm-2) to ablate germanium from a single crystal target. The substrate temperature during cleaning and deposition ranged from 300 to 500°C showing this to be a low temperature process. The films were analyzed using cross-section and plan-view transmission electron microscopy and high-resolution transmission electron microscopy. These films show the initial stages of epitaxial growth and Ge/Si interface with absence of an intermediate oxide layer. The significant reduction in substrate temperature for the formation of high quality epitaxial films opens up many new areas of applications requiring reduced thermal-budget processing.