In this paper we investigate axial p-n junction GaN nanowires grown by plasma-assisted MBE, with particular attention to the effect of Mg doping on the device characteristics of individual nanowire LEDs. We observe that single-nanowire LEDs produce measureable band-gap electroluminescence for a significant fraction of devices only when a thin AlGaN electron blocking layer is incorporated into the device structure near the junction. This observation and the low external quantum efficiency of the devices indicate that the primary non-radiative loss mechanism is the overflow of electrons from the n-type region through the p-type region and directly into the p-side contact. This effect is exacerbated by low p-type doping activity and Schottky-like contacts, which were confirmed by I-V measurements of the p-regions in junction nanowires as well as nanowires doped with Mg only. Our observations also show that diode-like I-V characteristics are observed even when an ideal p-n junction is absent.
Citation: Journal of Electronic Materials
Pub Type: Journals
Gallium Nitride, Nanowires, Molecular Beam Epitaxy, LEDs