Optical and electrical properties of Mn-doped GaAs grown by molecular-beam epitaxy

Abstract

An isolated acceptor impurity is shown to be responsible for the ∼113‐meV deep luminescence band which is frequently seen in GaAs layers grown by molecular‐beam epitaxy. We establish that this center, which is also observed in melt‐grown and solution‐grown GaAs and which has often been associated with the presence of native defects, is due to Mn. The luminescence arises from donor‐acceptor and conduction‐band–acceptor recombination involving holes bound at the Mn acceptor. Electron paramagnetic resonance on Mn‐doped layers shows that Mn is incorporated as an isolated defect with cubic symmetry. This result, coupled with the suppression of Mn‐associated luminescence and electrical activation under Ga‐rich growth conditions, indicates that Mn is incorporated primarily as a substitutional acceptor on Ga sites. Hole concentrations scale with Mn source temperature in a manner consistent with arrival‐rate‐controlled incorporation from a Knudsen effusion source. Room‐temperature hole concentrations up to the 10¹⁸‐cm⁻³ level can be achieved while maintaining excellent surface morphology. This suggests that Mn will be a useful dopant in the growth of junction structures by molecular‐beam epitaxy.