Near-Ultraviolet InGaN/GaN Light-Emitting Diodes Grown on Patterned Sapphire Substrates

Abstract

We describe the microstructure and optical properties of near-ultraviolet InGaN-GaN light-emitting diodes (LEDs) fabricated onto conventional and patterned sapphire substrates (PSSs) using metalorganic chemical vapor deposition. The PSS LED with an optimized hole depth (1.5 µm) shows an improvement of the room-temperature photoluminescence intensity by one order of magnitude compared with that of the conventional LED. As much as a 63% increased light emission intensity of the PSS LED was obtained at a forward current of 20 mA. For a typical lamp-form PSS LED (at 20 mA), the output power and external quantum efficiency were estimated to be 10.4 mW and 14.1%, respectively. The increase of the output power could be partly due to the improvement of the internal quantum efficiency upon decreasing the dislocation density, which was further confirmed by the transmission-electron-microscopy and etch-pit-density studies for the GaN-on-PSS samples. Moreover, the emitted light scattering at the GaN/PSS interface could also contribute to the enhancement of light extraction efficiency.

Growth and characterization of InGaN-based light-emitting diodes on patterned sapphire substrates

“…The PSS sample was prepared with parallel grooves (ridge: 2 mm; trench: 3 mm) along the (1 1 2 0) direction with different groove depths. Details of the PSS fabrication process are given elsewhere [11]. During the MOCVD growth, the trimethylgallium, trimethylindium and ammonia were used as the Ga, In and N precursors.…”

Growth and characterization of 380-nm InGaN/AlGaN LEDs grown on patterned sapphire substrates

“…A reduced dislocation density will result in an increase in the total compressive stress at room temperature because dislocations are known to relax stress. The in-grown dislocations directly over substrates can be slightly relaxed stress but will be less relaxed over the hole due to dislocation-free region as examined by transmissionelectron-microscopy measurements [11]. Fig.…”

Light‐emitting diodes fabricated on nanopatterned sapphire substrates by thermal lithography

“…However, the external quantum efficiency of the LEDs is generally low owing to the total internal reflection of the generated light. Therefore, patterned sapphire substrates (PSSs) in microsize are used to improve the light extraction efficiency [1,2]. Recently, nanopatterned sapphire substrates (nano-PSSs) have been used [3].…”