Visualization of the depleted layer in nanoscaled pn junctions on Si(011) surfaces with the use of scanning tunneling microscopy

We demonstrate that the microscopic variation of the bulk electronic properties of nanoscaled pn junctions formed on Si(001) surface is clearly visualized with the use of scanning tunneling microscopy/scanning tunneling spectroscopy (STM/STS). The STM measurement reveals that it is possible to distinguish among the n-type the p-type and the depleted p-type regions. It is shown that the contrasts between the regions strongly depend on the bias voltage for the STM measurement. Especially, for the negative sample bias voltage, it is observed that the width of the depletion layer gets wider with decreasing the sample bias voltage. We will discuss the origin of the bias voltage dependence of the STM image in terms of a metal-insulator-semiconductor structure model. It is also shown that the current imaging tunneling spectroscopy image can also visualize three regions of the nanoscaled pn junctions. (C) 1999 Elsevier Science B.V. All rights reserved.