Nippon Mining Co., Ltd.

Atsushi Kodama

Kazuhiko Suga

Akihito Yokohata

Hiroshi Kurita

A Gunn diode in which the conversion efficiency can be improved without lowering the reliability, by reducing the dead zone while maintaining n.sup.+ nn.sup.+ structure. In this Gunn diode, the donor impurity concentration in the n-type active layer is graded along a direction perpendicular to a contact plane between the n-type active layer and the n.sup.+ -type layers, and an average concentration gradient of the donor impurity concentration in the n-type active layer simultaneously satisfies the following two inequalities: G&gt;(A.sub.1 N/L)exp(-NL/S.sub.1) and G&lt;(A.sub.2 N/L)exp(-NL/S.sub.2), where L is a thickness of the n-type active layer, N is an average concentration of the donor impurity, S.sub.1 =0.87.times.10.sup.12 cm.sup.-2 is a constant, S.sub.2 =1.32.times.10.sup.12 cm.sup.-2 is a constant, A.sub.1 =2.0 is a constant, and A.sub.2 =9.0 is a constant.

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Toda, Japan

Atsushi Kodama