Abstract
Nowadays, ultraviolet light emitting diodes (UVLEDs) have aroused great interest in past few years for their promising application in adhesive curing, security identification and solid-state lighting etc. In gallium nitride (GaN) based LEDs, the patterned substrates and vertical devices' structure both played pivotal roles in elevating devices' performance. In this work, vertical near-UV-LEDs (405 nm) on different layers of carbon nanotube (CNT) patterns were fabricated by laser lift off (LLO), compared with the conventional lateral counterparts. The LLO threshold energy was reduced by CNTs layers. Although conventional lateral LEDs (LLEDs) exhibited highest external quantum efficiency (EQE) on 2CNTs pattern, the EQE of 3CNTs vertical LEDs (VLEDs) surpassed after LLO. The intrinsic physics mechanism, including: internal quantum efficiency (IQE), light extraction efficiency (LEE), Shockley-Read-Hall (SRH) recombination, radiative recombination and Auger effects, were analyzed by ‘ABC model’, Raman spectrum, X-ray Diffraction (XRD) and temperature dependence photoluminescence (TDPL).
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