n-Type and p-type co-doping for optimizing turn-on and threshold fields of SiC towards enhanced field emission properties

Abstract

Turn-on field (E_to) and threshold electric field (E_thr) are regarded as typical indexes for fabricating better field emission (FE) devices. Although doping is an efficient strategy to enhance the FE properties, the reasons for the effect of various types of dopants on E_to and E_thr values are unknown. In this paper, lanthanum (p-type) and nitrogen (n-type) co-doped SiC nanowires (LN-SiC NWs) were prepared using a two-step method, and exhibited enhanced FE properties with reduced E_to and E_thr values of 0.938 V µm⁻¹ and 3.077 V µm⁻¹, respectively. A series of characterization studies and DFT calculation results revealed the internal reasons for the enhanced FE properties via n-type and p-type dopant co-doping. The E_to value is influenced by the total amount of emitted electrons, and n-type N doping involving more valence electrons could provide more charge carriers for the CB to increase it. Therefore, n-type N doping could reduce the E_to value. The E_thr value is influenced by the band gap, and n-type N doping and p-type La doping could alter the hybridization states of the CB and VB for narrowing the band gap. Therefore, n-type and p-type co-doping could enhance the FE properties of LN-SiC NWs. This work provides theoretical guidance for understanding the enhanced FE properties as well as the effect of the dopant type on reduced E_to and E_thr values.