Negative magnetoresistance in Si atomic-layer-doped GaAs

Magnetoresistance of a Si atomic-layer-doped (δ-doped) GaAs is measured to study the transport properties of the δ-doped structure. The magnetoresistance decreases as the temperature is lowered and the depth of the δ-doped layer, i.e., the distance between the surface and the δ-doped layer, becomes less than 300 nm. Negative magnetoresistance is observed below 80 K in a sample having a doping density of 1.67×10¹² cm⁻² and a δ-doped layer depth of 40 nm. The conduction channel in the δ-doped structure consists of two parts, the quantized states in the conduction band and the impurity band. The origin of the negative magnetoresistance is suggested to be the conduction in the inhomogeneous potential due to localized impurity potential.