Characterization of Ge1-x-ySixSny Ternary Alloys - Comparison of UHV-CVD and Gas Source MBE Growth

Electrical, structural, and materials characteristics are reported for Ge1-x-ySixSny ternary alloys grown by UHV-CVD and gas source MBE. Composition and local bonding configuration are determined by XPS. Crystalline structural characteristics and relaxation of film strain were measured with X-ray diffraction. Temperature-dependent Hall-effect measurements show highly conductive layers although care must be exercised to account for parallel conduction through the substrate. Deep level transient spectroscopy shows two electron traps at low temperature in Ge1-x-ySixSny p-i-n diodes grown by UHV-CVD while samples grown by GS-MBE show only one, 10× weaker trap. The dark currents for both UHV-CVD and GS-MBE diodes exhibit an activation energy of Ea=0.40 eV at high temperature while the reverse bias leakage current in these films increases with increasing Sn content.