Abstract: A field effect semiconductor device which utilizes a 2DEG and is composed of a semi-insulating GaAs substrate; an i-type GaAs active layer; a superlattice structure layer which comprises a first i-type AlAs thin layer, a GaAs thin layer doped with an Si atomic plane, and a second i-type AlAs thin layer, these thin layers forming a GaAs quantum well; and n-type AlGaAs layer; and electrodes for source, drain, and gate.

Abstract: High electron mobility heterojunction semiconductor devices provided with a means to cause exposure of the electron source layer thereof to an electromagnetic wave allows modulation, adjustment and the like of the characteristics thereof even after completion of the production thereof, thus realizing a considerable magnitude of flexibility in the characteristics as well as considerably different modes in various embodiments, including field effect transistors which allow modulation of threshold voltage etc., connection channels or capacitors having a smaller resistance, programmable memory devices, image sensors. In addition, the high electron mobility heterojunction semiconductor devices can have a much higher operation speed than those available in the prior art.