Effect of Strains and V-Shaped Pit Structures on the Performance of GaN-Based Light-Emitting Diodes
Open Access
Abstract
Strains and V-shaped pits are essential factors for determining the efficiency of GaN-based light-emitting diodes (LEDs). In this study, we systematically analyzed GaN LED structures on patterned sapphire substrates (PSSs) with two types of growth temperature employed for prestrained layers and three different thickness of n-type GaN layers by using cathodoluminescence (CL), microphotoluminescence (PL), and depth-resolved confocal Raman spectroscopy. The results indicated that V-pits formation situation can be analyzed using CL. From the emission peak intensity ratio of prestrained layers and multiple quantum wells (MQWs) in the CL spectrum, information regarding strain relaxation between prestrained layers and MQWs was determined. Furthermore, micro-PL and depth-resolved confocal Raman spectroscopy were employed to validate the results obtained from CL measurements. The growth conditions of prestrained layers played a dominant role in the determination of LED performance. The benefit of the thick layer of n-GaN was the strain reduction, which was counteracted by an increase in light absorption in thick n-type doped layers. Consequently, the most satisfactory LED performance was observed in a structure with relatively lower growth temperature of prestrained layers that exhibited larger V-pits, leading to higher strain relaxation and thinner n-type GaN layers, which prevent light absorption caused by n-type GaN layers.Keywords
This publication has 43 references indexed in Scilit:
- GaN substrate and GaN homo-epitaxy for LEDs: Progress and challengesChinese Physics B, 2015
- High-Performance Blue InGaN Laser Diodes With Single-Quantum-Well Active LayersIEEE Photonics Technology Letters, 2007
- The Roles of Structural Imperfections in InGaN-Based Blue Light-Emitting Diodes and Laser DiodesScience, 1998
- Dislocation generation in GaN heteroepitaxyJournal of Crystal Growth, 1998
- High-quality InGaN MQW on low-dislocation-density GaN substrate grown by hydride vapor-phase epitaxyJournal of Crystal Growth, 1998
- Group III nitride semiconductors for short wavelength light-emitting devicesReports on Progress in Physics, 1998
- Thick GaN Epitaxial Growth with Low Dislocation Density by Hydride Vapor Phase EpitaxyJapanese Journal of Applied Physics, 1997
- Nitride-based semiconductors for blue and green light-emitting devicesNature, 1997
- Crystalline structure of AlGaN epitaxy on sapphire using AlN buffer layersApplied Physics Letters, 1994
- Improvements on the electrical and luminescent properties of reactive molecular beam epitaxially grown GaN films by using AlN-coated sapphire substratesApplied Physics Letters, 1983