Improvement of the Optical and Electrical Performance of GaN-Based Light-Emitting Diodes (LEDs) Using Transferrable ZnSnO3 (ZTO) Microsphere Monolayers

Abstract

We report on the formation of transferable microspheres monolayers consisting of ZnSnO3 (ZTO) synthesized via fast ethanol precipitation and their application to GaN-based light-emitting diodes (LEDs) to improve device performance. ZTO microspheres with diameters of 820 +/- 20 nm (ZTO-1), 910 +/- 10 nm (ZTO-2), and 1200 +/- 10 nm (ZTO-3) were synthesized and arrayed to form a monolayer using polydimethylsiloxane (PDMS) and a unidirectional rubbing method. ZTO-1, ZTO-2, and ZTO-3 monolayers exhibited optical transmittance percentages of 94.4%, 92.98%, and 87.09% at 450 nm, respectively. Effects of ZTO monolayers on the light extraction efficiency of LEDs were evaluated using LED chips sized 800 mu m X 800 mu m. LEDs with a ZTO-3 monolayer as a top layer had a light extraction efficiency of similar to 144%, relative to regular LEDs, as well as improved electrical properties, as evidenced by a decrease in V-turn on of similar to 0.6 V and a decrease in R-on by 0.036 k Omega XPS analysis indicated that the improvement in the electrical properties of LEDs with ZTO monolayers is due to the presence of graphene-like carbon bonds present in carbon residue that remains on the surface of the LED after removal of polymer. In terms of light extraction, ZTO monolayers effectively guided light generation from active regions in LEDs toward air, which was confirmed by three-dimensional finite-difference time-domain simulations.