DETERMINATION OF SEMICONDUCTOR SURFACE PROPERTIES BY MEANS OF PHOTOELECTRIC EMISSION

Methods for determining the electronic energy levels at and near the surface of a semiconductor with the help of experimental energy distributions of photoelectrically emitted electrons are described. Information can be obtained about the type of optical transitions responsible for the yield near threshold of clean surfaces and the significance of the photoelectric threshold, about the work function, electron affinity and ionization energy of the surface, as well as the total amount of band bending near the surface. These quantities completely characterize the energy diagram of a semiconductor surface. The above information is obtained without any assumption being made about the photoelectric emission process. It is shown that photoemission out of surface states with a density as low as 1 state per 100 surface atoms can, in principle, be measured, provided the semiconductor does not have a large concentration (> 1017 cm-3) of impurity states in the bulk. © 1969.