| 摘要 |
A homojunction or a heterojunction is formed to a channel layer (15) between a substrate (10) and the channel layer, a substrate side depletion layer (22) is extended to the channel layer (15) from the side of the substrate (10), and layers (13; 13a, 13b) operating as both substrate side depletion layer generating layers and back gate layers are provided for performing back-gate biasing by carriers generated by irradiation of light on the channel layer (15). On the front plane side of the channel layer (15), a barrier layer (16) wherein a band gap is wider than that of the channel layer (15), one of the carriers generated by light is permitted to run on the channel layer (15) and the other carrier to stay or blocked is provided. The front side of the channel layer (15) is provided with a front side depletion layer generating layer (17) wherein a front side depletion layer (21) is extended from the front side to the channel layer (15), and an element is turned off by bringing the front side depletion layer (21) into contact with a substrate side depletion layer (22) when light is not being applied and by closing a current path inside the channel layer (15). |
