论文标题:纤锌矿氮化物量子阱中极化子能量
Energy of a Polaron in a Wurtzite Nitride Quantum Well
论文作者
论文导师 赵凤岐,论文学位 硕士,论文专业 凝聚态物理
论文单位 内蒙古师范大学,点击次数 116,论文页数 24页File Size789K
2007-06-05论文网 http://www.lw23.com/lunwen_102669272/
nitride quantum well;; polaron;; ground state energy;; transition energy
近年来,纤锌矿氮化物材料由于具有禁带宽度大、击穿电场高、电子饱和速度高、热导率大、物理化学性能稳定等特殊的物理性质逐渐引起人们的关注。与此同时,电子与声子间的相互作用对半导体及其构成的低维结构的性质起着重要的作用。因此,纤锌矿氮化物半导体材料构成的量子阱结构中极化子的研究具有重要的意义。 本文采用Lee-Low-Pines(LLP)变分方法研究了纤锌矿氮化物(GaN/Al_xGa_(1-x)N)量子阱材料中自由极化子的能级,给出自由极化子基态能量、第一激发态能量和第一激发态到基态的跃迁能量与量子阱宽度和量子阱深度变化的函数关系。研究结果表明,自由极化子基态能量、第一激发态能量和跃迁能量随着阱宽L的增大而开始急剧减小,然后缓慢下降,最后接近于GaN中3维值。基态能量和第一激发态到基态的跃迁能量随着量子阱深度的增加而逐渐增加,窄阱时这一趋势更明显。纤锌矿氮化物量子阱中电子-声子相互作用对能量的贡献比较大,这一值(约40meV)远远大于闪锌矿(GaAs/Al_xGa_(1-x)As)量子阱中相应的值(约3meV)。因此讨论氮化物GaN/Al_xGa_(1-x)N量子阱中电子态问题时应考虑电子-声子相互作用。
Recently, wurtzite nitride semiconductors are taking more attentions of many researchers because of their characters such as wider energy gap, higher break-through electric field, quicker electron saturation velocity, larger heat conductance and more steady capabilities of physics and chemistry. Furthermore, the electron-phonon interaction is found strongly influence on the character of semiconductors and their low-dimensional structures. Therefore, the researches of polaron in wurtzite nitride quantum well structure are more meaningful. In this paper, the energy levels of free polarons in the wurtzite nitride (GaN/AlxGa1-xN)quantum well structure are studied by using Lee-Low-Pines (LLP) transition. The ground state, first excited state and transition energies from first excited state to ground state are calculated as a function of well width (L) and depth (V0). The results indicate that the ground state, first excited state and transition energies rapidly decrease with increasing the well width at smaller L, but slowly at larger L, and finally approach to the bulk value of GaN. The ground state, first excited state and transition energies all slowly increase with increasing V0, and it is more visible in narrow well. It is also found that the contribution of electron-phonon interaction in wurtzite nitride quantum well structure is very large, the value (about 40meV) is much larger then that (about 3 meV) in zinc-blende (GaAs/Al_xGa_(1-x)As) quantum well structure. Therefore, the contribution of electron-phonon interaction in wurtzite nitride quantum well structure should be considered when the election state in nitride GaN/Al_xGa_(1-x)N quantum well is discussed.
|
