Optimal Silicon Doping Layers of Quantum Barriers in the Growth Sequence Forming Soft Confinement Potential of Eight-Period In0.2Ga0.8N/GaN Quantum Wells of Blue LEDs

• Published in: Nanoscale research letters Vol. 12; no. 1; pp. 1 - 8
• Main Authors: Wang, Hsiang-Chen, Chen, Meng-Chu, Lin, Yen-Sheng, Lu, Ming-Yen, Lin, Kuang-I, Cheng, Yung-Chen
• Format: Journal Article
• Language: English
• Published: New York Springer US 09.11.2017; Springer Nature B.V; SpringerOpen
• Subjects: Barriers; Blue light-emitting diodes; Breakdown; Chemistry and Materials Science; Confinement; Doping; Electron microscopy; Gallium nitrides; Image resolution; Image transmission; InGaN/GaN quantum wells; Injection; Injection current; Interfaces; Light emitting diodes; Localization; Localization of carriers; Materials Science; Metalorganic chemical vapor deposition; Molecular Medicine; Nano Express; Nanochemistry; Nanoscale Science and Technology; Nanotechnology; Nanotechnology and Microengineering; Organic chemicals; Organic light emitting diodes; Photoluminescence; Photons; Quantum wells; Quantum-confined Stark effect; Sapphire; Silicon; Silicon doping; Soft confinement potential; Stark effect; Substrates; Transmission electron microscopy; Soft confinement potential; Localization of carriers; Blue light-emitting diodes; Silicon doping; InGaN/GaN quantum wells; Quantum-confined Stark effect
• ISSN: 1931-7573; 1556-276X
• DOI: 10.1186/s11671-017-2359-3

The features of eight-period In 0.2 Ga 0.8 N/GaN quantum wells (QWs) with silicon (Si) doping in the first two to five quantum barriers (QBs) in the growth sequence of blue light-emitting diodes (LEDs) are explored. Epilayers of QWs’ structures are grown on 20 pairs of In 0.02 Ga 0.98 N/GaN superlattice acting as strain relief layers (SRLs) on patterned sapphire substrates (PSSs) by a low-pressure metal-organic chemical vapor deposition (LP-MOCVD) system. Temperature-dependent photoluminescence (PL) spectra, current versus voltage ( I - V ) curves, light output power versus injection current ( L - I ) curves, and images of high-resolution transmission electron microscopy (HRTEM) of epilayers are measured. The consequences show that QWs with four Si-doped QBs have larger carrier localization energy (41 meV), lower turn-on (3.27 V) and breakdown (− 6.77 V) voltages, and higher output power of light of blue LEDs at higher injection current than other samples. Low barrier height of QBs in a four-Si-doped QB sample results in soft confinement potential of QWs and lower turn-on and breakdown voltages of the diode. HRTEM images give the evidence that this sample has relatively diffusive interfaces of QWs. Uniform spread of carriers among eight QWs and superior localization of carriers in each well are responsible for the enhancement of light output power, in particular, for high injection current in the four-Si-doped QB sample. The results demonstrate that four QBs of eight In 0.2 Ga 0.8 N/GaN QWs with Si doping not only reduce the quantum-confined Stark effect (QCSE) but also improve the distribution and localization of carriers in QWs for better optical performance of blue LEDs.