Scanning tunneling microscopy/spectroscopy as an atomic-resolution dopant profiling method in Si

Abstract

The ability of scanning tunneling microscopy and spectroscopy (STM/STS) as a dopant profiling method in Si is demonstrated. We have developed two different methods. One is a simultaneous measurement of potential and dopant atom distributions by conventional STM/STS. Actually acceptor and donor atoms were distinctly detected and the local potential variation was observed at p-n junctions on atomically-flat hydrogenated Si(111) substrates. The comparison between the measured dopant atom and potential distributions at a p-n junction revealed that the potential profile was significantly affected by the fluctuation of dopant atom distributions. The other is a quantitative measurement of carrier distributions by resonance electron tunneling (RET) spectroscopy. The RET peak energy of C60 molecules placed on oxidized Si(001) surfaces was measure by STS and the resulting value systematically varied depending on the doping level of the substrates, enabling us to measure carrier density profiles across p-n junctions. © 2008 IOP Publishing Ltd.