AFM and temperature-dependent photoluminescence studies of the degree of localization induced by quantum-dot like states in InGaN single quantum well light emitting diodes grown by MOCVD on (0 0 0 1) sapphire

• Published in: Journal of crystal growth 2004-12, Vol.272 (1), p.449-454
• Main Authors: Florescu, D.I., Ramer, J.C., Merai, V.N., Parekh, A., Lu, D., Lee, D.S., Armour, E.A.
• Format: Article
• Language: English
• Subjects: A1. Atomic force microscopy; A3. Metalorganic chemical vapor deposition; A3. Quantum wells; Applied sciences; B1. Nitrides; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronics; Exact sciences and technology; Iii-v semiconductors; Light-emitting devices; Materials science; Nanoscale materials and structures: fabrication and characterization; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optoelectronic devices; Photoluminescence; Physics; Quantum dots; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2004.08.076

In this work, we investigate the surface morphology and temperature-dependent photoluminescence of InGaN/GaN single quantum well light-emitting diodes grown by metal organic chemical vapor deposition on (0 0 0 1) sapphire and their correlation with the degree of localization induced by quantum-dot-like states in these structures. By varying the growth parameters and based on atomic force microscopy and 300 K photoluminescence findings, a high density of quantum-dot-like states was achieved in our InGaN structures. More specifically, atomic force microscopy reveals 10–50 nm diameter dots with a density in the range of 2–30×10 9 cm 2. At the same time, the room temperature photoluminescence signal shows at least a 10× intensity increase compared to similar structures without the dots. Temperature-dependent photoluminescence spectra display the anomalous “S-shaped” behavior of the PL energy peak for the structures where the quantum-dot-like states are present. Concurrently, a change in the temperature range of the photoluminescence emission that outlines the “S-shape” is observed for samples with different dot density and size. A strong correlation of the “S-shape” lower inflection point with the degree of localization induced by the presence of quantum-dot-like states is proposed. Applying the principles and observations discussed, a thermally robust 465 nm single quantum well light-emitting diode with an unpackaged chip-level output power in the 5.5–6.0 mW range and forward voltage