Ionization rates in 〈111〉 and 〈100〉 germanium are determined experimentally. The ionization rates obtained are expressed as α=2.72×106 exp(−1.1×106/E), β=1.72×106 exp(−9.37×105/E) for 〈111〉 and α=8.04×106 exp(−1.4×106/E), β=6.39×106 exp(−1.27×106 /E) cm−1 for 〈100〉 where α and β are ionization rates for electrons and holes, respectively, and E is the electric field. Hole- to electron-ionization-rate ratios of 〈100〉 Ge are found to be greater than those of 〈111〉 Ge. The multiplication noise power of Ge avalanche photodiodes calculated by using the ionization rates obtained shows good agreement with experimental results.

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An H3PO4–H2O2–H2O solution is studied for possible use in the etching of germanium. The solution can be roughly classified into two ternary regions according to its etching characteristics: a (with a low H2O2 concentration) and b (with a high H2O2 concentration). Solutions in region b provide reproducible smooth and uniform surfaces. This solution can be used with SiO2 films and photoresists as a preferential etching mask material without dissolution or separation. It is suitable for processing germanium devices.

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