Contact free potential mapping by vibrating capacitor
The contact free vibrating capacitor method is a valuable tool for investigating the surface potentials of solid surfaces. The purpose of the present article is to summarize the theory and capabilities of the vibrating capacitor method, especially scanning vibrating capacitor pictures in the electronics. After a brief review some results will be discussed, such as a contact potential map taken from a printed circuit board, a surface potential map from a biased ceramic thick film circuit and some results from silicon solid state devices and solar cells. Potential maps contain a lot of information concerning the surface conditions, included the inhomogeneities of the technology, bias and other additional excitation. These potential maps may help in the development, quality control and defect analysis
Surface potential mapping: comparison of the vibrating capacitor and the SPV method
Abstract Surface potential maps are very important for characterisation of insulator covered and bare semiconductor surfaces. Contactless methods use capacitive coupling. Vibration (vibrating capacitor) and light (SPV, surface photo voltage method) are used for the surface excitation. Both methods give information about the surface potential, and are sensitive to the surface charge, too. This article discusses the differences and similarities between the methods, concerning theory, application and evaluation of the results. Several surface potential maps are presented and evaluated too.
Surface photovoltage spectroscopy of thin films
The surface photovoltage (SPV) spectrum due to subband‐gap illumination of thin films is theoretically studied. It is shown that this SPV is inherently sensitive to buried interfaces just as it is sensitive to the external semiconductor surface. The different contributions to the SPV from all the optically active gap states present within a sample, consisting of a bulk substrate covered by a thin film, are analyzed. Analytical expressions are obtained in the low illumination intensity and the depletion approximation regime. The evolution of the SPV spectrum with film thickness is examined and is found to depend on both site and population of the gap states. Three modes of evolution are found, according to the relative importance of gap state population changes with film thickness. These modes are confirmed by a numerical simulation of a thin film of pseudomorphic InAlAs on InP substrates and by experiments conducted on the same system. The approach is also applied to the InP/In2O3 system, revealing gap st...