The electronic and magnetotransport properties of epitaxial p-(In,Mn)As/n-InAs heterojunctions have been studied. The junctions were formed by depositing ferromagnetic (In,Mn)As films on InAs (100) substrates using metal-organic vapor phase epitaxy. The current-voltage characteristics of the junctions have been measured from 78 to 295 K. At temperatures below 150 K, ohmic current dominate transport at low bias, followed by defect-assisted tunneling current with increasing bias. At high forward bias, junction transport is dominated by diffusion current. The magnetoresistance of the junctions was measured as a function of forward bias and applied magnetic field. The magnitude and field dependence of the longitudinal magnetoresistance depend directly on the junction transport mechanism. Under high bias, a magnetoresistance of 15.7% at 78 K and 8% at 295 K in a 4400 Oe field was measured in an In0.96Mn0.04As/InAs junction. At 78 K, the high bias magnetoresistance increases linearly with magnetic field from 1000 to 4600 Oe. (c) 2005 American Vacuum Society.