Study of the potential distribution in a forward-biased silicon diode using electrostatic force microscopy

Abstract

Electrostatic force microscopy was used to study the potential distribution in a forward-biased epitaxial-diffused n +-n-p-p + silicon diode. Distributions of potential and capacitance were determined across the cleaved surface, which intersected the layers in the diode structure. Variations in the surface potential and capacitance were preliminarily measured with a submicrometer spatial resolution and were used to determine the position and width of the n-p junction; the distribution of applied forward bias in the diode was also assessed. It is shown that an additional potential barrier for injected charge carriers may exist in the vicinity of the n +-n junction in the diode under consideration. For an injection-current density exceeding 100 mA/cm2, the voltage drop across this barrier becomes comparable with the voltage variations across the operating n-p junction.