title: Effects of overgrown p-layer on the emission characteristics of the InGaN/GaN quantum wells in a high-indium light-emitting diode.
abstract: The counteraction between the increased carrier localization effect due to the change of composition nanostructure in the quantum wells (QWs), which is caused by the thermal annealing process, and the enhanced quantum-confined Stark effect in the QWs due to the increased piezoelectric field, which is caused by the increased p-type layer thickness, when the p-type layer is grown at a high temperature on the InGaN/GaN QWs of a high-indium light-emitting diode (LED) is demonstrated. Temperature- and excitation power-dependent photoluminescence (PL) measurements are performed on three groups of sample, including 1) the samples with both effects of thermal annealing and increased p-type thickness, 2) those only with the similar thermal annealing process, and 3) those with increased overgrowth thickness and minimized thermal annealing effect. From the comparisons of emission wavelength, internal quantum efficiency (IQE), spectral shift with increasing PL excitation level, and calibrated activation energy of carrier localization between various samples in the three groups, one can clearly see the individual effects of thermal annealing and increased p-type layer thickness. The counteraction leads to increased IQE and blue-shifted emission spectrum with increasing p-type thickness when the thickness is below a certain value (20-nm p-AlGaN plus 60-nm p-GaN under our growth conditions). Beyond this thickness, the IQE value decreases and the emission spectrum red shifts with increasing p-type thickness.
authors.affiliation: Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan.
authors.forename: Chih-Yen
authors.initials: CY
authors.lastname: Chen
authors.forename: Chieh
authors.initials: C
authors.lastname: Hsieh
authors.forename: Che-Hao
authors.initials: CH
authors.lastname: Liao
authors.forename: Wei-Lun
authors.initials: WL
authors.lastname: Chung
authors.forename: Hao-Tsung
authors.initials: HT
authors.lastname: Chen
authors.forename: Wenyu
authors.initials: W
authors.lastname: Cao
authors.forename: Wen-Ming
authors.initials: WM
authors.lastname: Chang
authors.forename: Horng-Shyang
authors.initials: HS
authors.lastname: Chen
authors.forename: Yu-Feng
authors.initials: YF
authors.lastname: Yao
authors.forename: Shao-Ying
authors.initials: SY
authors.lastname: Ting
authors.forename: Yean-Woei
authors.initials: YW
authors.lastname: Kiang
authors.forename: Chih-Chung C C
authors.initials: CC
authors.lastname: Yang
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Hu
mesh_terms: D002138:Calibration; D003198:Computer Simulation; D004867:Equipment Design; D005708:Gallium / Q000737:chemistry*; D006358:Hot Temperature; D007204:Indium / Q000737:chemistry*; D008027:Light; D049449:Luminescence; D055095:Optics and Photonics; D010777:Photochemistry / Q000379:methods*; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D007204:Indium; C473348:gallium nitride; D005708:Gallium