Thin film micro-scaled cold cathode structures of undoped and Si-doped AlN grown on SiC substrate with low turn-on voltage

The field emission characteristics of the AlN thin films with micro-scaled cold cathode structures are tested in the high vacuum system. The aluminum nitride (AlN) thin films with a thickness of about 100 nm are prepared on the n-type 6H-SiC (0001) substrate at 1100 ℃ by metal organic chemical vapor deposition (MOCVD) under low pressure. The I–V curves and surface micro-images of undoped and Si-doped AlN films are investigated. From the I–V and Fowler–Nordheim plots, it can be seen that the Si-doped AlN shows better field emission characteristics compared with the undoped AlN sample. The obtained turn-on field is 6.7 V/μm and the maximum emission current density is 154 mA/cm² at 69.3 V for the Si-doped AlN film cathode after proper surface treatment. It is proposed that the relatively low electric resistivity of Si-doped AlN films is significant for electron migration to the surface region, and their rougher surface morphology is beneficial to a higher local electric field enhancement for the field emission.