Fabrication of bulk and epitaxial germanium field emitter arrays by dry etching techniques

[Display omitted] ► High aspect-ratio field emitter arrays on bulk silicon and on bulk germanium were fabricated entirely by dry etching. ► The process has been applied on epitaxial germanium to fabricate field emitter arrays. ► Good emission properties were found in terms of electric field threshold, field enhancement, reproducibility, time stability. We present the fabrication and characterization of novel high density field emitter arrays (FEAs) on CVD-grown epitaxial germanium on (001) silicon. In particular we propose a heterostructure made up of silicon as substrate and of germanium as active layer, exploiting the infrared transparency of Si and the infrared sensitivity of Ge to realize a semi-transparent photo-assisted electron beam source. We used a completely dry etching process in fluorinated gases (SF6) due to its significant under-etching for both silicon and germanium. High aspect ratio silicon and germanium FEAs, with minimum tip radii of 25nm and 40nm, respectively, and lower aspect ratio Ge/Si FEAs with minimum tip radii of 50nm were fabricated. The realized FEAs show good emission behavior with field emission characteristics straight related to tip geometry: low electric field threshold for silicon and germanium tips (