Techniques are provided that can impart sufficient electrical conductivity to a semiconductor crystal exhibiting low doping efficiency for silicon atoms, such as InGaAs, by implanting only a small amount of silicon atoms. Such a semiconductor wafer may include a first semiconductor crystal layer, a second semiconductor crystal layer exhibiting a conductivity type that is different from the first layer, a third semiconductor crystal layer exhibiting the conductivity type of the first layer and having a larger band gap than the second semiconductor crystal layer, and a fourth semiconductor crystal layer exhibiting the conductivity type of the first layer and having a smaller band gap than the third semiconductor crystal layer. The fourth semiconductor crystal layer contains a first element that generates a first carrier of a corresponding conductivity type and a second element that generates a second carrier of a corresponding conductivity type.
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