Alternating-Current InGaN/GaN Tunnel Junction Nanowire White-Light Emitting Diodes

The
current LED lighting technology relies on the use of a driver to convert
alternating current (AC) to low-voltage direct current (DC) power,
a resistive p-GaN contact layer to inject positive
charge carriers (holes) for blue light emission, and rare-earth doped
phosphors to down-convert blue photons into green/red light, which
have been identified as some of the major factors limiting the device
efficiency, light quality, and cost. Here, we show that multiple-active
region phosphor-free InGaN nanowire white LEDs connected through a
polarization engineered tunnel junction can fundamentally address
the afore-described challenges. Such a p-GaN contact-free
LED offers the benefit of carrier regeneration, leading to enhanced
light intensity and reduced efficiency droop. Moreover, through the
monolithic integration of p-GaN up and p-GaN down nanowire LED structures on the same substrate, we have
demonstrated, for the first time, AC operated LEDs on a Si platform,
which can operate efficiently in both polarities (positive and negative)
of applied voltage.