Multi‐color light emitting diode using polarization‐induced tunnel junctions

A multi-color light emitting diode (LED) using two distinct active regions connected via a tunnel junction was grown by rf-plasma-assisted molecular beam epitaxy. The LED is contacted through n-type layers, one of which provides efficient contact to a p-type layer via a second tunnel junction. The tunnel junctions used in the structure use the high polarization fields found in the III-nitrides material system to narrow the depletion width of the junction. Two peaks at 405 nm and 490 nm are observed in the electroluminescence spectrum of the LED, and current-voltage characteristics indicate a turn-on voltage of roughly 7.5 V and dynamic series resistance of 19 Ω at 80 mA for a 300 μm square device. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)