Abstract
Abstract Improving current injection into r- and m-planes of nanowires (NWs) is essential to realizing efficient GaInN/GaN multiple quantum shell (MQS) NW-based light-emitting diodes (LEDs). Here, we present the effects of different p-GaN shell growth conditions on the emission characteristics of MQS NW-LEDs. Firstly, a comparison between cathodoluminescence (CL) and electroluminescence (EL) spectra indicates that the emission in NW-LEDs originates from the top region of the NWs. By growing thick p-GaN shells, the variable emission peak at around 600 nm and degradation of the light output of the NW-LEDs are elaborated, which is attributable to the localization of current in the c-plane region with various In-rich clusters and deep-level defects. Utilizing a high growth rate of p-GaN shell, an increased r-plane and a reduced c-plane region promote the deposition of indium tin oxide layer over the entire NW. Therefore, the current is effectively injected into both the r- and m-planes of the NW structures. Consequently, the light output and EL peak intensity of the NW-LEDs are enhanced by factors of 4.3 and 13.8, respectively, under an injection current of 100 mA. Furthermore, scanning transmission electron microscope images demonstrate the suppression of dislocations, triangular defects, and stacking faults at the apex of the p-GaN shell with a high growth rate. Therefore, localization of current injection in nonradiative recombination centers near the c-plane was also inhibited. Our results emphasize the possibility of realizing high efficacy in NW-LEDs via optimal p-GaN shell growth conditions, which is quite promising for application in the long-wavelength region.
Highlights
Over the past few decades, group III nitride semiconductors, with fundamental bandgaps covering a broad spectral range, have been developed for solid-state lighting and lasing technologies [1,2,3,4]
The difference in height was attributable to the edge effect during n-GaN core growth at high temperature since precursors diffused from the adjacent region were limited due to the gap or step existing between the NW template and surrounding dummy wafers
We have systematically investigated GaInN/GaN multiple quantum shell (MQS) NW-lightemitting diodes (LEDs) by controlling the growth conditions of the p-GaN shell and investigating optical characteristics
Summary
Over the past few decades, group III nitride semiconductors, with fundamental bandgaps covering a broad spectral range, have been developed for solid-state lighting and lasing technologies [1,2,3,4]. Despite the progress in epitaxial growth, limited results on fabrication and electrical performance of MQS NW-LED chips have been presented [30, 31] Several issues such as the blue-shift tendency with increasing the injection current [32, 33], current localization at the c-plane apex region of NWs [12], and the red emission under low current injection [34, 35] need to be resolved. We explored the emission characteristics of NW-LEDs with different p-GaN morphologies, aiming to improve the uniformity of ITO deposition and thereupon current injection into r- and m-planes of the NWs. The MQS active structures and n-GaN cores were prepared under identical growth conditions to minimize the probability of different In contents among the samples. The emission features of the NW-LEDs were discussed based on the scanning transmission electron microscopy (STEM) results
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
