SCANNING TUNNELING SPECTROSCOPY ON CLEAVED SILICON PN-JUNCTIONS

Scanning tunneling microscope (STM) I- Vexperiments in air on freshly cleaved Sipn junctions, are presented. It is shown that the interaction between the tip and the sample may cause the whole structure to behave as a solid-state device. With the tip in the vicinity of the pn junction the junctions depletion layer may pinch off the tip current, in much the same way as the increasing gate bias of a junction field-effect transistor reduces the channel current. Under other bias conditions, the STM tip may locally forward bias the pn junction causing a sharp increase in the tip current. Using this mode of operation the pn junction was localized to within 50 nm. A dependence of the tip-sample I- V characteristic on the local impurity concentration of the sample was also observed. A simple qualitative model consisting of a diode, which represents the tip-Si junction, in series with the resistance of the underlying material, explains these measurements. © 1990, American Vacuum Society. All rights reserved.