Nanofabrication of gallium nitride photonic crystal light-emitting diodes

Abstract

a b s t r a c tWe describe a comparison of nanofabrication technologies for the fabrication of 2D photonic crystal structures on GaN/InGaN blue LEDs. Such devices exhibit enhanced brightness and the possibility of controlling the angular emission profile of emitted light. This paper describes three nano lithography techniques for patterning photonic crystal structures on the emitting faces of LEDs: direct-write electron beam lithography, hard stamp nanoimprint lithography and soft-stamp nanoimprint lithography with disposable embossing masters. In each case we describe variations on the technique as well as its advantages and disadvantages. Complete process details have been given for all three techniques. In addition, we show how high performance GaN dry etch techniques, coupled with optical process monitoring can transfer resist patterns into underlying GaN material with high fidelity.

Emission characteristics of photonic crystal light-emitting diodes

“…This was done in order to better understand the advantages and disadvantages offered by different fabrication techniques and to see which technique could become the mainstay of commercial LED manufacturing operations. The results of our study on the nanofabrication of PhC LEDs has been published elsewhere [18]. Here we present our findings from measurements carried out on PhC LEDs fabricated by us.…”

“…We believe that proper spreading metal deposition as well as the choice of our electrode design were factors that led to the excellent emission uniformity. Further details on device fabrication can be found in our earlier publication related to the fabrication of these devices [18].…”

Further enhancement of light extraction efficiency from light emitting diode using triangular surface grating and thin interface layer

“…In fabricating the structure, the annealing temperature and capillary action time are two critical factors that are to be carefully controlled to ensure repeatability of the desired dimensions. Fabrication and analysis of nanogratings on conventional GaN LEDs have been reported [26][27][28][29]. Such nano-thick structures are used in organic LEDs [30,31].…”

Nanoimprint lithography for nanodevice fabrication

“…However, this is also a good fit for low cost optical lithography, so most nanoimprint lithography work has been on improving the performance of LEDs through the incorporation of nanoscale patterning. For example, many groups have demonstrated the integration of photonic crystals on top of LEDs by nanoimprint lithography, improving light output by as much as 25 % [ 10 , 44 , 45 ]. To limit etching damage, Truong et al directly imprinted titanium oxide photonic crystals using sol gel titania as an imprint resist with a soft poly[(3-mercaptopropyl) methylsiloxane] (PMMS) mold specifically designed to allow solvent diffusion through the mold during the curing process [ 46 ].…”