We consider hopping transport in a dilutely doped sheet of Si donors in GaAs. Samples are constructed as multiple δ layers, spaced significantly farther apart than the average, in-plane donor separation. In this system we have determined activation energies and studied the positive magnetoresistance effect quantitatively. We provide a detailed examination of the negative-magnetoresistance effect that stems from quantum interference of neighboring hopping paths.

• Received 4 December 1989

DOI:https://doi.org/10.1103/PhysRevB.41.8477