Optiacl characterization of ZnxCd1-xSe/Znx’Cdy’Mg1-x’-y’Se quantum wells structures.

• Main Authors: Jhih-wei Lin, 林智偉
• Other Authors: Ying-Sheng Huang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/93082266720265974071

碩士 === 國立臺灣科技大學 === 電子工程系 === 97 === Contactless electroreflectance (CER) was used to characterize the possible optical transitions in a Zn0.46Cd0.54Se/Zn0.24Cd0.25Mg0.51Se multiple quantum well (MQW) and a Zn0.48Cd0.52Se/Zn0.24Cd0.18Mg0.58Se asymmetric coupled quantum well (ACQW) structures grown on (001) semi-insulating InP by molecular beam epitaxy for midinfrared device applications. The CER spectra revealed a wide range of the possible optical transition in the QW structures. The transition energies were obtained using a fitting process based on the first derivative of a Lorentzian lineshape. The ground state transitions were assigned by comparing with the PL emission signals taken from the same structures. In order to assign the remaining transitions, calculations were performed based on the envelope function approximation, considering that the well was doped. The values for the effective masses were obtained from a linear interpolation of the binary compounds. A value for the conduction-band band offset of ΔEc = 0.75  0.05 ΔEg was used. The identified transitions corresponded to the symmetry allowed and symmetry forbidden but parity allowed transitions. The calculation matched with the measured values. From these data, the intersubband transitions could be estimated and were further confirmed by Fourier transform infrared absorption measurements. The results demonstrate the potential of using CER as a technique for the contactless and nondestructive characterization of the wide band gap II-VI QW structures for mid-IR intersubband device applications.