Dependence of Schottky Barrier Height on Donor Concentration

Abstract

Schottky barrier heights of Au contacts to n‐type Si with either etch‐polished or vacuum‐cleaved interfaces are independent of donor concentration within an experimental uncertainty of about ±0.05 eV for 10¹⁴ cm⁻³≤N_D≤10¹⁹ cm⁻³. Within the same uncertainty and over the same doping range, barrier heights determined from capacitance using the standard formula are equal to those determined from photoemission thresholds. A theory for deducing barrier heights from photoemission thresholds that includes the effects of tunneling and image force is presented. The results are interpreted in terms of a simple model for the interface, which is characterized by the thickness d and dielectric constant κ′ of the interfacial film and the density n_ss of interface states. The insensitivity of the barrier height to the quantity of space charge leads to the following limit on the interfacial parameters: $${\text{(k′/d)+1.8×10}}^{\text{−6}}{n}_{\mathrm{ss}}{\text{≥3.8×10}}^8\hspace{0.17em}{\mathrm{cm}}^{\text{−1}}$$ for d in cm, and n_ss in cm⁻² eV⁻¹.