Enhancement of the light output power of InGaN/GaN light-emitting diodes grown on pyramidal patterned sapphire substrates in the micro- and nanoscale

Abstract

Sapphire substrates were patterned by a chemical wet etching technique in the micro- and nanoscale to enhance the light output power of InGaN/GaN light-emitting diodes (LEDs). InGaN/GaN LEDs on a pyramidal patterned sapphire substrate in the microscale (MPSS) and pyramidal patterned sapphire substrate in the nanoscale (NPSS) were grown by metalorganic chemical vapor deposition. The characteristics of the LEDs fabricated on the MPSS and NPSS prepared by wet etching were studied and the light output powers of the LEDs fabricated on the MPSS and NPSS increased compared with that of the conventional LEDs fabricated on planar sapphire substrates. In comparison with the planar sapphire substrate, an enhancement in output power of about 29% and 48% is achieved with the MPSS and NPSS at an injection current of 20 mA, respectively. This significant enhancement is attributable to the improvement of the epitaxial quality of GaN-based epilayers and the improvement of the light extraction efficiency by patterned sapphire substrates. Additionally, the NPSS is more effective to enhance the light output power than the MPSS.

High Responsivity in GaN Ultraviolet Photodetector Grown on a Periodic Trapezoid-Column Patterned Sapphire Substrate

“…For the same area of the sapphire substrate, a reduced geometrical size of sapphire patterns can increase the number of patterns, and thus increase the opportunity for light scattering from the PSS. (30,31) In addition, a geometrical pattern of a suitable shape and sidewall angle on the sapphire substrate can also increase the reflection of unabsorbed photons resulting in more photogenerated carriers as embedded reflectors, in accordance with Snell's law.…”

Analysis of loss mechanisms in InGaN solar cells using a semi-analytical model

“…[11][12][13][14] Other optoelectronic devices have been more inclined to employ pattern sapphire substrates (PSS) to enhance light extraction. [18][19][20][21][22] Furthermore, despite costly and complicated growth and fabrication process, there have been reports proposing using diffraction grating on the back of the device for InGaN solar cells to enhance the optical absorption, 23 which combines the textured surface and reflecting substrate. These reports are also consistent with our findings here.…”

Enhanced light extraction in tunnel junction-enabled top emitting UV LEDs

“…The sample was annealed at 860 °C for 90 s under N 2 ambient to form nano-sized Ni clusters. [21][22][23][24] The self-assembled Ni nano-clusters were used as nanoscale etch masks for inductively coupled plasma reactive ion etching (ICP-RIE) of both Devices with and without surface roughening were compared on the same sample by avoiding Ni deposition in half of the sample area. The electroluminescence (EL) spectrum and emission power were measured on-wafer from the top surface of the devices at room temperature using a calibrated Ocean Optics USB 2000 spectrometer coupled with a fiber optic cable.…”