Contact Potential Measurements on Cleaned Germanium Surfaces

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Abstract
The contact potential of the (110) face of the n and p regions of an n‐p germanium crystal was measured in a vacuum of less than 10−9 mm Hg using a Kelvin bridge technique. The n and p regions were so doped that their resistivities were 0.058 and 0.33 ohm‐cm, respectively. If there had been no surface states the difference in work function would have been 0.34 ev. The argon‐cleaned surface exhibited a difference of 0.002(±0.004) ev. An exposure of as little as 0.4×10−7 mm‐min of oxygen increased the difference to 0.013 ev. A difference as large as 0.018 ev was observed after a 28×10−7 mm‐min exposure. After 56×10−7 mm‐min the difference was reduced to 0.000(±0.005) ev. These results are discussed in terms of several surface state distributions.