Self-consistent modelling of tunnelling spectroscopy on III-V semiconductors

- We model tunnelling spectroscopy measurements within a finite element device simulator.
- Tip-induced bending is included and arbitrary realistic tip shapes are used in the modelling.
- We compare simulated spectra of III-V semiconductors and the tip induced band bending against other models.
- We include image force correction in the model.
- The tunnelling current increases by 3-6 orders of magnitude when image force correction is used.

A simulation methodology to model tunnelling spectroscopy measurements based on the Price-Radcliffe formalism has been developed within a finite element device simulator. The tip-sample system is modelled self-consistently including tip-induced bending and realistic tip shapes. The resulting spectra of III-V semiconductors are compared against experimental results and a model based on the Bardeen tunnelling approach with very good agreement. We have found that the image force induced barrier lowering increases the tunnelling current by three orders of magnitude when tunnelling to the sample valence band, and by six orders of magnitude when tunnelling to the sample conduction band. The work shows that other models which use a single weighting factor to account for image force in the conduction and valence band are likely to be underestimating the valence band current by three orders of magnitude.