Traditional LEDs have already transformed the lighting and display industries because to their greater stability and efficiency. Compared to conventional devices like incandescent light bulbs and cathode tubes, LEDs are typically stacks of semiconductor thin films with lateral dimensions on the order of millimeters. LEDs with diameters as small as a few micrometers are necessary for upcoming optoelectronic applications like virtual and augmented reality. Micro or submicron scale LEDs (LEDs) must maintain the many superior qualities that conventional LEDs already have, including highly stable emission, high efficiency and brightness, super low power consumption, and full-color emission, while being approximately one million times smaller in area to enable much more compact display. If such LEDs can be monolithically grown on Si for integration with complementary metal-oxide-semiconductor (CMOS) electronics, they will also open the door for considerably more potent photonic circuits. 

However, such LEDs are still difficult to find, particularly in the green to red emission wavelength region. InGaN quantum well (QW) thin films are patterned into devices with dimensions in the micro scale using etching techniques in the traditional top-down method for creating LEDs. Thin-film InGaN QW-based LEDs have received a lot of attention because of the many advantageous characteristics of InGaN, including effective charge carrier transport and wavelength tunability across the entire visible range, but up until now they have been plagued by problems like sidewall etching damage that gets worse as the device size shrinks. Additionally, they experience wavelength/color instability brought on by the polarization fields, a problem for which non-polar and semi-polar InGaN and photonic crystal cavities have been suggested but haven’t yet proven successful.

In a new paper published in Light Science & Application, researchers led by Professor Zetian Mi from the University of Michigan in Ann Arbor, USA, have developed III-nitride submicron-scale green µLEDs that overcome these barriers all at once. These µLEDs are synthesized with selective area plasma-assisted molecular beam epitaxy. In stark contrast to the conventional top-down approach, the µLEDs here consist of arrays of nanowires, each of which is only 100~200 nm in diameter and tens of nanometers apart. Such a bottom-up approach intrinsically avoids sidewall etching damage.

 


Post time: Nov-11-2022