Studying magnetic diodes with a GaMnAs layer formed by pulsed laser deposition

A new design for diode heterostructures with (Ga, Mn)As ferromagnetic layers is experimentally investigated. The diode structures are fabricated using a combination of metal-organic chemical vapor deposition (MOCVD) epitaxy and pulsed laser deposition and contain (Ga, Mn)As/$n$-InGaAs heterojunctions. The electrical properties of the diodes in a magnetic field applied perpendicular to the $p$–$n$ junction are examined. The negative magnetoresistance observed at temperatures of $<$ 50 K (below the (Ga, Mn)As Curie temperature) is attributed to a decrease in the carrier scattering caused by ferromagnetic ordering and in the potential barrier at the (Ga, Mn)As/$n$-InGaAs interface. The observed negative magnetoresistance depends nonmonotonically on the forward bias with a maximum in the voltage region close to the $p$–$n$-junction potential barrier height. The maximum can be caused by the decisive contribution of the spin-dependent resistances of the (Ga, Mn)As layer and (Ga, Mn)As/$n$-InGaAs interface to the total resistance of the structure. It is found that the dependence of the magnetoresistance on the external magnetic field is hysteretic due to the influence of tensile stresses in the (Ga, Mn)As layer grown on top of a relaxed In$_{x}$Ga$_{1-x}$As buffer layer with an indium content of $x\approx$ 0.1.