444 nm InGaN light emitting diodes on low-defect-density $(11\bar{2}2)$ GaN templates on patterned sapphire

Abstract

Efficient InGaN-based 444 nm blue light-emitting diodes (LEDs) were fabricated on low-defect-density semipolar GaN templates grown on patterned r-sapphire. At 20 A/cm2, the packaged LEDs exhibited a light output power of 2.9 mW (17.8 mW at 100 A/cm2) and a record peak external quantum efficiency of 6.4% showing a negligible efficiency droop and blue shift with drive currents up to 100 A/cm2. In addition, we demonstrated light extraction simulations for the template, which showed that the structured pattern is not only beneficial for limiting the defect propagation but also increases the light extraction by 29% compared with GaN layers grown on planar substrates.

Semipolar (10-11) GaN growth on silicon-on-insulator substrates: Defect reduction and meltback etching suppression

“…Other dark lines inclined at 75°to the [11][12][13][14][15][16][17][18][19][20] direction can also be seen, as evidenced in Fig. 5(a), corresponding to dislocations, or clusters of dislocations, appearing only after coalescence has occurred between neighboring stripes.…”

“…The aim is to create a pyramid at the beginning of growth in order to bend all dislocations nucleating on the inclined Si facets. 13,19 This growth stage is referred to as stage A. Continuing growth under the same condition for 1500 s leads to the formation of small c facets as shown in Fig.…”

“…In their approach, the growth takes place on inclined v-shaped (111) facets etched on the silicon substrate, 12 the inclination of which determines the orientation of the GaN semipolar epilayer grown thereon. Accordingly, various semipolar orientations were achieved, including (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN layer on the r-plane patterned sapphire substrate (PSS), 13,14 (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN on the patterned (113) Si substrate, 15 and (20-21) GaN on the (114) 1°off patterned Si substrate. 16 In the case of sapphire substrates, several methods have been implemented to reduce the dislocation density in the semipolar GaN layers; in particular, the so-called 3-steps growth on PSS 13 results in a record threading dislocation density in the mid-10 7 cm 2 range and a BSF density of around 100 cm −1 , establishing the current state of the art.…”

“…(20)(21) semipolar GaN and InGaN quantum well were also demonstrated on similarly patterned sapphire substrates. 17 Recently, semipolar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) 550 nm yellow/green 18 and 444 nm blue InGaN light-emitting diodes (LEDs) 19 and semipolar (20)(21) GaN and InGaN LEDs 20 were demonstrated on sapphire templates using this defect filtering method.…”

Demonstration of Efficient Semipolar 410 nm Violet Laser Diodes Heteroepitaxially Grown on High-Quality Low-Cost GaN/Sapphire Substrates

“…To date, however, semipolar LDs have been achieved only on costly small-area semipolar bulk GaN substrates, limiting their wide use. Realization of low-cost semipolar LDs by heteroepitaxial growth is appealing, − but the efficiency of semipolar LEDs grown on foreign substrates remains poor because of the high dislocation defect density. − The best external quantum efficiency (EQE) of semipolar blue LEDs is only 6%, which is still much lower than that of semipolar blue LEDs on a bulk GaN substrate or conventional c-plane blue LEDs. On the other hand, the development of semipolar LDs on foreign substrates is even more challenging.…”