The role of mesa size in nano‐structured green AlGaInN light‐emitting diodes

Abstract

The mesa width of green light‐emitting diodes (LEDs) was scaled from the micrometer to the nanometer range. The devices were patterned by electron beam lithography and dry etching and contained up to 100 parallel nano‐stripe LEDs connected to one common contact area. The mesa width was varied over 1 µm, 200 nm, and 50 nm. The LEDs were characterized electrically and optically, and the peak emission wavelength was found to depend on the lateral structure size. Light emission from the patterned region was found to be 4 times brighter than from the un‐patterned regions. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Study on Light Extraction from GaN-based Green Light-Emitting Diodes Using Anodic Aluminum Oxide Pattern and Nanoimprint Lithography

“…Much progress has been made in LEE by nanostructures on emission surface of green LEDs 1 2 3 4 5 6 7 8 9 10 11 . These structures are fabricated by electron beam lithography (EBL) 1 2 , laser interference lithography (LIL) 3 4 , nanoimprint lithography (NIL) 5 6 7 8 9 , and anodic aluminum oxide (AAO) 10 11 . The LEE enhancements for the patterned green LEDs in the above reports range 19% to 25 times compared to the planar ones, depending on the nanostructure parameters and LEE measuring conditions.…”

Experimental and Modeling Investigations of Miniaturization in InGaN/GaN Light-Emitting Diodes and Performance Enhancement by Micro-Wall Architecture

“…The increased ratio of perimeter-to-area in the smaller LEDs leads to improved heat dissipation and reduced self-heating, hence the temperature in the LED device is decreased ( Kim et al, 2012 ; Horng et al, 2015 ). Moreover, the light extraction through the sidewalls is improved with diminished LED size, which contributes to the improvement of the LED performance ( Stark et al, 2011 ).…”

“…The peak wavelength is about 450 nm and is not shifted when the size is reduced from 180 to 45 μm, as indicated in Figure 3C . However, it is worth noting that when the LED size is further reduced to the nanoscale, the blue shift in the EL curve can be anticipated due to reduced energy band tilting caused by the strain relaxation in the smaller LED device ( Demangeot et al, 2002 ; Wu et al, 2008 ; Stark et al, 2011 ).…”

“…Thereafter, we can conclude the effect of size-reduction ( E ) for InGaN/GaN LEDs as following: where C ( x ) is the alleviated current crowding effect ( Ge et al, 2019 ), P ( x , y ) is the improvement achieved by the increased perimeter-to-area ratio, including improved thermal dissipation and light extraction ( Choi et al, 2003a ; Choi et al, 2003b ), T ( x , y ) is the reduced self-heating and improved heat distribution ( Gong et al, 2010 ; Ploch et al, 2013 ), S ( x , y ) is the enhancement owing to the strain relaxation ( Demangeot et al, 2002 ; Tao et al, 2012 ; Ge et al, 2019 ), and N ( x , y ) is the possible negative effect due to the increased nonradiative recombination ( Gong et al, 2010 ; Stark et al, 2011 ), surface recombination ( Jin et al, 2001 ), and current leakage induced by etching damage and impurities during fabrications ( Jin et al, 2000 ; Stark et al, 2011 ). A more detailed quantitative analysis of the above factors is needed to determine the dominant ones and great precautions must be undertaken to avoid degradation in devices during the growth and fabrication processes for smaller LEDs.…”

Interdigital Structure Enhanced the Current Spreading and Light Output Power of GaN-Based Light Emitting Diodes

“…Although vertical LED is considered as a good alternative to solve the current crowding issue and improve the output power for high-power and high-efficiency lighting applications [19], it also costs high because of complicated bonding processes required [20]. By researching previously published literatures of interdigits and MESAs of GaN [21][22][23][24][25][26][27][28][29][30][31][32], we noticed there is still no systematic and in-depth studies on the mechanism of mesa size and structures. Particularly, the major problem of the high-power LEDs is the current crowding under high current injection.…”