The ordinary semiconductor diode displays unusual properties at high frequencies. It is observed that at high frequencies the rectification changes polarity. The phenomenon is explainable by short-duration carrier multiplication; the result being that more charge is reclaimable than is stored. This is seen as a negative resistance; i.e. when the diode is driven by high frequencies, it becomes active and can amplify, oscillate or switch.
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LINE-MAYER et al. (1963) studied this question.