Role of substrate quality on the performance of semipolar (112¯2) InGaN light-emitting diodes

Abstract

We compare the optical properties and device performance of unpackaged InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) emitting at ∼430 nm grown simultaneously on a high-cost small-size bulk semipolar (112¯2) GaN substrate (Bulk-GaN) and a low-cost large-size (112¯2) GaN template created on patterned (101¯2) r-plane sapphire substrate (PSS-GaN). The Bulk-GaN substrate has the threading dislocation density (TDD) of ∼105 cm−2–106 cm−2 and basal-plane stacking fault (BSF) density of 0 cm−1, while the PSS-GaN substrate has the TDD of ∼2 × 108 cm−2 and BSF density of ∼1 × 103 cm−1. Despite an enhanced light extraction efficiency, the LED grown on PSS-GaN has two-times lower internal quantum efficiency than the LED grown on Bulk-GaN as determined by photoluminescence measurements. The LED grown on PSS-GaN substrate also has about two-times lower output power compared to the LED grown on Bulk-GaN substrate. This lower output power was attributed to the higher TDD and BSF density.

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

“…22Þ blue LEDs, which exhibited similar values (1.8 nm shift) in a similar range of drive currents. 18) Generally, to our knowledge, these values outperform previously reported blue LEDs grown on semipolar ð11 22Þ, as shown in the comparative summary in Table I. [18][19][20][21][22] Ray-tracing simulations were performed using a commercial software package 23) to evaluate the difference in the LEE between the 3S-PSS template and the planar template structures.…”

“…18) Generally, to our knowledge, these values outperform previously reported blue LEDs grown on semipolar ð11 22Þ, as shown in the comparative summary in Table I. [18][19][20][21][22] Ray-tracing simulations were performed using a commercial software package 23) to evaluate the difference in the LEE between the 3S-PSS template and the planar template structures. Ray-tracing simulations use the laws of geometrical optics to analyze the behavior of a statistical population of rays propagating in systems with feature sizes larger than the wavelength of light in the materials.…”

Reduction of basal plane defects in (11-22) semipolar InGaN/GaN MQWs fabricated on patterned (113) Si substrates by introducing AlGaN barrier layers

“…Prior to the MOCVD growth, patterning of Si substrates was performed. Stripe grooves with (111) Si facets extending along the direction were fabricated by a conventional photolithography technique. At first, a 100 nm‐thick thermally oxidized SiO 2 mask on (113) Si substrate was fabricated into a stripe pattern by ICP‐RIE.…”

“…There are some experimental results of the remarkable high power LEDs with several semipolar crystal planes grown on bulk GaN substrates . However, semipolar LEDs fabricated on sapphire substrates have shown lower output powers compared to those of the LEDs grown on bulk GaN substrates . Growth of semipolar GaN films on foreign substrates or patterned substrates is not an easy task because the inherent high density of threading dislocations and stacking faults degrades the optical and electrical properties of the devices .…”

Spatially-resolved optical and structural properties of semi-polar $$\mathrm{(11}\bar{2}\mathrm{2)}$$ Al x Ga1−x N with x up to 0.56

“…These electric fields are the cause of the quantum-confined Stark effect (QCSE), which reduces the quantum efficiency, and its effect increases with increasing AlN fraction. Growth of Al x Ga 1− x N in non- or semi-polar orientations is of interest for removing or decreasing the effect of the QCSE, as already successfully employed for visible devices using the InGaN alloy system 7 – 9 . However, moving away from the polar orientation leads to a high density of extended defects such as stacking faults (SFs) and misfit dislocations in addition to threading dislocations (TDs) also present in c -orientated hetero-epitaxial nitride materials 10 – 12 .…”