  We report on the design, fabrication, and characterization of GaN interband
tunnel junction showing forward tunneling characteristics. We have achieved
very high forward tunneling currents (153 mA/cm2 at 10 mV, and 17.7 A/cm2 peak
current) in polarization-engineered GaN/InGaN/GaN heterojunction diodes grown
by plasma assisted molecular beam epitaxy. We also report the observation of
repeatable negative differential resistance in interband III-Nitride tunnel
junctions, with peak-valley current ratio (PVCR) of 4 at room temperature. The
forward current density achieved in this work meets the typical current drive
requirements of a multi-junction solar cell.
