Photoluminescence study of InAsPSb bulk epilayers on InAs substrates

• Main Authors: De-Lun Wang, 王德棆
• Other Authors: 林浩雄
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/98240893008666503102

碩士 === 臺灣大學 === 電機工程學研究所 === 95 === We have successfully grown InAsPSb samples on n+ (100) InAs substrates by gas-source molecular beam epitaxy. Samples with rich arsenic composition which are located away from miscibility gap in quaternary composition plane show better surface morphology and crystal quality. Power dependent and temperature dependent photoluminescence measurements were performed on these samples. Because of the existence of miscibility gap, PL results of these samples can be roughly classified as three different groups. For sample C1898-C1900, whose compositions lie inside the miscibility gap, low temperature PL transition was dominated by band-tail state recombination; on the other hand, the high temperature PL spectra show wide FWHM values and the FWHM values increase proportionally to the root of temperature. Gaussian shape spectra and temperature independent PL peak energy behavior imply deep level transition which can be explained by configuration-coordinate model. With sample’s compositions outside the miscibility gap, temperature dependent PL has “inverse S-shape” behavior which due to the tail-states resulted from alloy fluctuation. The PL peak energy follows Varshni law and is close to calculated bandgap value as temperature increasing. Theoretically calculated band to band PL emission spectrum fits well with experimental results suggest a band-edge recombination with samples grown outside miscibility gap at high temperature. Finally, for samples with composition near miscibility gap boundary, we can observe weak peak signal located at the high energy side whose energy was quite close to calculated results at room temperature. We conjectured that the deep level transition and band to band transition exist in high temperature. At last we attribute the low temperature activation energy to the delocalization energy of tail-states. For the sample’s compositions inside miscibility gap, the high temperature activation energy can be explained by configuration-coordinate model.