Tunneling Through MnAs Particles at a GaAs P+ N+ Junction

In this article we examine tunneling through MnAs particles at a GaAs p+ n+ junction. We grew the device structures by molecular beam epitaxy on semi-insulating GaAs (001) substrates, with the n+ (5× 1018 cm-3 Si) and p+ (2× 1019 cm-3 Be) layers grown at 580 °C. At the p+ n+ junction, we grew a 30 nm layer of random alloy Ga1-x Mnx As at 250 °C. In situ annealing the Ga1-x Mnx As transforms to thermodynamically stable MnAs particles in a GaAs matrix. Magnetization measurements show that the MnAs particles are superparamagnetic with a distribution of blocking temperatures that depends on the annealing protocol. The MnAs particles at the interface are imaged using atomic force microscopy of selectively etched, MnAs-topped nanocolumns. Current-voltage (IV) scans show that the presence of particles increases the forward bias current density. Low-temperature current-voltage (IV) scans confirm an increase in the forward bias current density due to tunneling through MnAs particles.