Effects of Antimony and Nirogen Incorporation into Self-assembled InAs/GaAs Quantum Dots

• Main Authors: Ren-Fong Huang, 黃任鋒
• Other Authors: Jenn-Fang Chen
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/64700624600812582607

碩士 === 國立交通大學 === 電子物理系所 === 93 === This thesis is divided into two topics, including optical properties of InAsSb/GaAs quantum dots and electric properties of InAsN/InGaAs Dots-in-well structure. The effect of Sb incorporaton into self-assembled InAs/GaAs quantum dots(QDs) is investigated by photoluminescence(PL) and atomic force microscope(AFM). Three samples with different QDs deposition of 2.0, 2.2 and 2.8ML, are grown by molecular beam epitaxy(MBE). Sb reacts in InAs/GaAs system as a surfactant, which increases the critical thickness from 1.68ML to 2.0ML at which the growth mode changes from two-dimentional(2D) to three-dimentional(3D) growth. The results of PL and AFM data show that QDs are divided into two groups, InAs-rich and InSb-rich. This fully demonstrates the phase separation of InAsSb QDs. With thickness of epi-layer increasing, density of InSb-rich QDs is higher. For small deposition of 2.0ML and 2.2ML, a large FWHM at 25K is observed, implying a poor uniformity of these QDs size. With temperature increasing, trasfer of electrons from InAs-rich QDs to InSb-rich QDs is easier. With spacing of QDs decreasing, the lower temperature is needed for electrons transfer. The effect of N incorporation into the InAs/InGaAs QDs is investigated by admittance spectroscopy, capacitance transients and deep-level transient spectroscopy. No traps are observed in the QDs sample without N incorporation. The emission time of electrons from QDs is less than 1E-6 sec at 18K. However, the QDs sample with the N(17%) incorporation directly into the QDs would introduce defect traps which cause the carrier depletion. The emission time for electrons from defect traps is about1E-3~1E-5 sec at 300K. The capture barriers Eσ=0.15eV, traps level Et=0.2~0.25eV and traps concentration Nt=1~2.8E15cm-3 are measured by DLTS. In comparison, in order to make depletion width W=0.25μm by C-V measurement and barriers Eσ=0.15eV, the traps concentration Nt=1.06E15cm-3 is needed.