The Study of Carrier Dynamics in Multi-Stacked InAs/GaAs Quantum Dots

• Main Authors: Fu-Yun Wang, 王福雲
• Other Authors: Der-Jun Jang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/36186502302857800081

碩士 === 國立中山大學 === 物理學系研究所 === 100 === This paper is using the Time-resolved Pump-Probe spectroscopy to study the quantum dots samples. The samples are InAs/GaAs multi-stacked quantum dots that with different spacer layer (10~30 nm). The stain between the InAs quantum dots and GaAs spacer layer that makes the valence band to split into heavy-hole and light-hole energy band. From the photoluminescence (PL), we see the heavy-hole and light-hole energy band are blue shift in InAs quantum dot, when the GaAs spacer layer decrease. We use the optic property of Pump-Probe spectroscopy of the change in the refraction index Δn to investigate the shift of heavy-hole energy band, when the GaAs spacer layer decrease. We see the heavy-hole energy band of GaAs is blue shift when the GaAs spacer layer decrease. When we change the pump energy, the TRPP spectroscopy signal will change from positive to negative. This is the band-filling effect changes the refraction index Δn , when the energy close to the GaAs heavy hole energy state. When the energy is above the GaAs heavy hole energy state, the TRPP signal is positive. When the excited carrier density decrease and the delay time increase, TRPP signal will change the positive value to negative value. These are band-gap renormalization and free-carrier absorption effect change the refraction index Δn, when the carrier density decrease.