Optical Investigation of GaN-based Quantum-confined Structure

• Main Authors: Yi-Ting Wang, 王薏婷
• Other Authors: Hao-Chung Kuo
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/64742976535544775171

碩士 === 國立交通大學 === 光電工程系所 === 93 === In this dissertation, two kinds of GaN-based quantum confined structure were studied. The first one was the effect of δ-TMIn-flow process on optical and materials properties in InGaN/GaN MQWs. The second one was the structural and optical studies on inverted pyramid-shaped GaN QDs grown on AlN nanoholes. First, the effects of δ-TMIn-flow process on optical and material properties in InGaN/GaN MQWs were investigated with XRD, TEM, PL and PLE measurement. According to TEM and XRD measurement, good layer periodicity and structural quality of the InGaN/GaN MQW were observed. And the In-rich clusters in the InGaN/GaN MQW were resided in both sample whether δ-TMIn-flow process or not. And from PL results, the PL peak energies were different at 10 K even though the same composition extracted from XRD measurement. From the FWHM results of PL measurement, In-rich clusters were more uniform in size of sample B as compared to sample A. And according to the PL and PLE measurement result, the larger values of σ, Ea and Stokes’ shift in sample B indicated that the δ-TMIn flow resulted in the increase the composition fluctuation in InGaN MQW regions and showed the stronger carrier localization effect. And the light output of the GaN LEDs with the δ-TMIn-flow process was increased up to 24% without obvious deterioration of interfacial abruptness. Second, we performed the structural and optical studies on inverted pyramid-shaped GaN QDs with dimensions of 40/40 nm (length/depth). The μ-PL measurements of these GaN QDs were performed over a temperature range from 80 to 300 K. Comparing with GaN bulk structure, the ground state of GaN QDs was blueshifted by 63 meV. PL emission peak energy did not change much in temperature range from 80 to 300 K, the energy gap shrinkage was just about 35 meV in the QD structures compared with 60 meV in GaN bulk materials. Finally we observed the narrowing of full-width at half maximum (FWHM) with increasing temperature to 100 K, this phenomenon can be attributed to carrier redistribution of different GaN QD sizes