Effect of Chemical Etches on the Fast Germanium Surface States

Simultaneous measurements of surface recombination velocity and added trapped charge density in the fast states as a function of surface potential were carried out on one and the same n-type filament which was subjected to three different etches: CP—4A, concentrated HNO3 and HF. Most measurements were performed at various temperatures. It was found that (a) the reproducibility of surface state parameters after successive treatments with CP—4A was excellent; (b) the influence of the different etches was surprisingly small, with one exception: the average capture probability cp for holes was found to undergo a more than threefold increase after treatment with HF; (c) the energy of the recombination center did not always decrease with increasing temperature, contrary to all previously reported measurements.