High-Performance GaN-Based Light-Emitting Diodes on Patterned Sapphire Substrate with a Novel Patterned SiO₂/Al₂O₃Passivation Layer

Abstract

GaN-based light-emitting diodes (LEDs) on patterned sapphire substrate (PSS) with a novel patterned SiO 2 /Al 2 O 3 passivation layer have been proposed and fabricated. Due to the excellent uniformity and compactness of atomic layer deposition (ALD) for the first Al 2 O 3 layer, a high passivation effect has been achieved. The second SiO 2 layer with patterned hemisphere arrays decreases the total internal reflection (TIR) and, hence, increases the light output power (LOP). With a 60 mA injection current, an enhancement of 21.6% in LOP was realized for the LED with an appropriately patterned SiO 2 /Al 2 O 3 passivation layer as compared with the conventional LED with a SiO 2 passivation layer.

Study of defects in LED epitaxial layers grown on the optimized hemispherical patterned sapphire substrates

“…19) Among these patterns, hemispherical PSS, which is widely applied to PSS applications, exhibits more potential to improve LED efficacy along with its effectiveness to reduce dislocation density. 20,21) As for the dimensions of the pattern, however, the radii of patterns are within 1.5 µm in general, 18,22,23) and larger patterns are almost intact in research. Such dimensional vacancy of patterns with radii exceeding 1.5 µm therefore needs to be further studied to realize higher light extraction efficiency.…”

Comprehensive Investigation of Electrical and Optical Characteristics of InGaN-Based Flip-Chip Micro-Light-Emitting Diodes

“…The indium tin oxide (ITO) in contact with the p-GaN layer served as the current spreading layer for enhancing the electric conductivity and current spreading over the device [ 12 ]. The micro-LED chip was encapsulated with a thin SiO 2 layer for passivation and for insulation to reduce electrical leakage [ 13 ]. Finally, the metal was applied (through openings in SiO 2 ) as the p-contact to ITO/p-GaN and the n-contact to n-GaN [ 14 ].…”

“…In general, R Auger is more significant at the high current densities, while R SRH is dominant at the low current densities (thus, under general operating conditions of micro-LED devices). In view of the high perimeter-to-area ratios of micro-LEDs, the trap-assisted surface non-radiative recombination occurring at mesa surfaces was also considered [ 3 ], setting the trap levels 0.46 eV above the valence band and 0.24 eV below the conduction band [ 25 ], and setting the surface recombination velocities (SRVs) for both electrons and holes ( v s,n and v s,p , respectively) around 1000 cm/s ( Table 1 ) [ 13 ]. Through electrical simulation under different biases, the spatial distributions of carrier concentrations, current flows, various recombination rates, and spontaneous emission rates as a function of bias, J–V characteristics, and electroluminescence (EL) and IQE as a function of bias can be analyzed.…”

Study on the Quantum Confinement of Photo-Generated Carriers in Quantum Wells

“…The longitudinal transport is affected by the quantum confinement effect, which is quite different from that in the horizontal direction [5]. In the light-to-electric situation, according to classical theory [5], carriers would relax to the ground state and be confined in low dimension materials due to the quantum effect, which is beneficial to recombination for injection carriers [6][7][8][9]. So MQWs is hard to be used in light-toelectric devices due to the low escape rate.…”