Abstract: An undoped Al.sub.0.22 Ga.sub.0.78 As layer, an undoped In.sub.0.2 Ga.sub.0.8 As electron-drifting layer, and an undoped GaAs electron-supplying layer are formed in order on a GaAs substrate. An impurity-doped layer .delta.-doped with Si donor is formed in the GaAs electron-supplying layer. An n-Al.sub.0.22 Ga.sub.0.78 As layer and n.sup.+ -GaAs cap layers are formed in order on the GaAs electron-supplying layer. A source electrode and a drain electrode are formed on the n.sup.+ -GaAs cap layers and a gate electrode is formed on the n-Al.sub.0.22 Ga.sub.0.78 As layer.

Abstract: A group III-V compound semiconductor doped with an impurity, having an undoped film of SiOx and a film for preventing the diffusion of Group V atoms (e.g., an SiN film) are formed on a crystal of Group III-V compound semiconductor in which the silicon in the SiOx film is diffused into the Group III-V compound semiconductor, thereby forming a doped layer.

Abstract: A method of doping a Group III-V compound semiconductor with an impurity, wherein after an undoped film of SiOx and a film for preventing the diffusion of Group V atoms (e.g., an SiN film) are formed in this order on a crystal of Group III-V compound semiconductor, the sample is subjected to at least one heat treatment to cause silicon in the SiOx film to diffuse into the Group III-V compound semiconductor, thereby forming a doped layer. Using this doped layer forming method, field-effect transistors, diodes, resistive layers, two-dimensional electron gas or one-dimensional quantum wires, zero-dimensional quantum boxes, electron wave interference devices, etc. are fabricated.