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 x 10(18) cm(-3) Si) and p(+)(2 x 10(19) cm(-3) Be) layers grown at 580 degrees C. At the p+n+ junction, we grew a 30 nm layer of random alloy Ga1-xMnxAs at 250 degrees C. In situ annealing the Ga1-xMnxAs 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. (c) 2006 American Vacuum Society.