Optical properties of InGaN Nano Disk on GaN nanorods

• Main Authors: Ming-Hui Yang, 楊名慧
• Other Authors: Tzu-Min, Hsu
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/06869843362918389084

碩士 === 國立中央大學 === 物理研究所 === 96 === This thesis investigates the optical properties of InGaN/GaN nanorods on Si(111) substrate grown by plasma-enhanced molecular beam epitaxy (PA-MBE). The structural properties of nanorods are explored by scanning electron microsope (SEM) and cathodoluminescence (CL). The optical emission properties of the InGaN/GaN nanorods are studied by photoluminescence (PL) as well as time-resolved photoluminescence (TRPL). The luminescence of InGaN layer can be proved emission at 500-750 nm by tuning the laser excitation energies above and below GaN band gap energy. The photoluminescence of InGaN layer also displays multiple peaks, we measure the luminescence at normal and 90o direction and confine with simple calculations to prove these peaks are originated from multi-beam interference, while the reflected planes are GaN/air and GaN/substrate interface. Two decay time constants are observed for InGaN layer in time-resolved photoluminescence measurements. After estimating their integrated intensity, we assume the shorter one is the lifetime of carriers near InGaN/air interface at lateral which can be measured at 90o direction and the longer one is the lifetime of carriers inside InGaN layer which can be measured at normal direction. Comparing with the lifetime of quantum wells, the reduced lifetime of InGaN layer on the nanorods is caused by effective suppressing the piezoelectric field due to strain relaxation. Growth of active layer on nanorods can effective reduces the density of defects and improves the spontaneous emission rate; the remained problem may be the nonradiative processes caused by the surface states.