Properties of Zinc-, Copper-, and Platinum-Doped Germanium

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Abstract
Hall effect and resistivity measurements have been made on a number of samples of single-crystal germanium containing additions of zinc, platinum, and copper. All three were found to be acceptors with energy of ionization 0.029, 0.040, and 0.036-ev electron volt, respectively. Measurements were made in the temperature range 15°K to about 400°K. All the Hall and resistivity curves showed a tendency to flatten out at the lowest temperatures, rather than to continue on an exponential curve. Possible explanations include (a) surface conductivity with low activation energy, (b) traces of low-ionization energy acceptors, (c) internal leakage due to imperfections or dislocations. Studies were made looking for acceptor states in the upper part of the forbidden band, such as have been found for gold. Evidence was found for a platinum acceptor level 0.2 ev below the conduction band and for a copper acceptor level just below the middle of the forbidden band.