| 摘要 |
PROBLEM TO BE SOLVED: To provide an element that can efficiently change a drain current with a small amount of holes. SOLUTION: An element is formed of a multilayer structure of a compound semiconductor. For a semiconductor substrate 1 and a buffer layer 2, a material having a band gap energy which passes the incident light beam is selected and for a channel layer 3, a material working as the light-absorbing layer is selected. An n-type impurity is doped to a barrier layer 4, and thereby the carrier electrons flow into the drain electrode 6 from the source electrode 5. The gap between both electrodes has a structure such that the surface spinning region 7 where the surface Fermi level is near the valence band disables existence of electrons within the channel immediately under such region in the non-irradiation condition of the light beam. Regarding the relationship of the energy among the barrier layer 4, a channel layer 3, and a buffer layer 2, the conductive band of the channel layer 3 is sufficiently lower than the other two layers and thereby electrons may be accumulated easily, the valence band almost does not generate energy difference between the barrier layer 4 and channel layer 3 and he buffer layer 2 has the energy which is identical to that of other two layers or the energy sufficient lower than that of these layers.
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