| AVS 58th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing Division | Thursday Sessions |
| Session EM+TF-ThM |
| Session: | Hybrid Electronic Materials and Interfaces |
| Presenter: | Ayelet Vilan, Weizmann Institute of Science, Rehovot Israel |
| Authors: | A. Vilan, Weizmann Institute of Science, Rehovot Israel R. Har-Lavan, Weizmann Institute of Science, Rehovot Israel O. Yaffe, Weizmann Institute of Science, Rehovot Israel P. Joshi, Weizmann Institute of Science, Rehovot Israel R. Kazaz, Weizmann Institute of Science, Rehovot Israel D. Cahen, Weizmann Institute of Science, Rehovot Israel |
| Correspondent: | Click to Email |
The Schottky-Mott model predicts that the eventual energy barrier formed when metal and semiconductor are brought into intimate contact, will be equal to the difference between the metal work function and the semiconductor's electron affinity (for n-type). 60 years of extensive experiments have clearly shown that this ideal picture, that seems to hold for wide bandgap ionic semiconductors such as ZnO, GaS etc., is far from being adequate for the more covalent narrow bandgap Si, Ge, InP, and GaAs. Following Bardeen, who attributed this deviation from the model to surface states energetically located within the semiconductor's forbidden gap, different explanation were raised as for the source of those surface states.
One commonly used model for surface states formation at the interface of semiconductor and metal is the intrinsic Metal Induced Gap State (MIGS) model, stating that gap states are inevitably formed due to the decay of metal electronic states' wavefunction into the semiconductor's bandgap.
We have examined the presence of such MIGS using Hg, which is one of the few metals that doesn't interact chemically with Si, as an electrode. Furthermore, in order to eliminate surface states which are just due to Si dangling bonds, we have used state of the art mixed molecular monolayers of hydroquinone and alcohols that were shown to be the best chemical passivation for Si surfaces.
Using alcohols of different alkyl chain lengths we succeeded to effectively change the electron affinity of the Si over 400 mV range while maintaining firm surface passivation. Current-voltage measurements of diodes formed that way, with Hg on organically modified n-Si surface, demonstrated near ideal Schottky-Mott characteristics with index of interface behavior S=0.9 (compared to a common value for Si S=0.1).