Improvement of Blue InGaN/GaN Multiple Quantum Wells with Graded Layers Silicon Doping Barrier

• Main Authors: YEH,PO-HSIEN, 葉柏顯
• Other Authors: Hsiang-Chen Wang
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/23k9zw

碩士 === 國立中正大學 === 光機電整合工程研究所 === 103 === The characteristics of 8 periods of In0.2Ga0.8N/GaN quantum wells (QWs) with part of silicon-doped barriers under high injection current for high optical performance of blue light-emitting diodes (LED) are explored. With the use of patterned sapphire substrate (PSS), QWs were deposited on 20 pairs of In0.02Ga0.98N/GaN strain relief layers (SRLs) by low pressure metal-organic chemical vapor deposition (LP-MOCVD) system. For various excitation energy of light above and below the bandgap of GaN barriers, room-temperature photoluminescence (RT-PL) spectra of all samples showed blue shifts in spectral peak energy on account of the decrease of quantum confined Stark effects (QCSE) in QWs with part of silicon-doped barriers. The enhancement of PL intensity and reduction of potential energy fluctuations in QWs with 4 silicon-doped barriers were found. There was observed that strong absorption intensity in the energy range from the bandgap energy of InGaN wells to the GaN barriers in 4-barrier-doped sample in room-temperature photoluminescence excitation (RT-PLE) spectra. This suggests that a deviation from the perfect regular rectangular shape of potential to blur interface of QWs was caused by out-diffusion indium from wells into barriers. It also results in relatively homogeneous distribution of injection carriers and reduction of the non-radiative Auger processes in sample with 4-barrier-doped silicon. Higher LED output power and larger external quantum efficiency (EQE) can be seen in 4-barrier-doped sample. The results reveal that part of silicon-doped barriers in 8 periods of InGaN/GaN QWs is applicable to high brightness of blue LEDs.