多层异质结构中的声学声子输运

Acoustic-phonon transmission in multilayer heterojunctions

在连续弹性近似下,采用转移矩阵方法,研究了由不同含Al浓度的异质结(GaAs/AlxiGa1-xiAs)所构成的对称多层异质结构中的声学声子输运性质.结果表明:该结构中的声子透射谱具有与同组分厚度超晶格(GaAs/AlAs)不一样的特征,具体体现在透射曲线振荡幅度与频率等方面;声子透射谱特征与对称异质结构中AlxiGa1-xiAs层的含Al浓度xi(i表示对称轴两边的第i层)的分布有很大的关系,具体表现为:当xi随i的增加而递减时,透射谱线除主波谷外较平滑;而当xi随i的增加而递增时,透射谱振荡明显增大,且主波谷被分裂.声子透射系数还依赖于异质结组分层的厚度,尤其是AlxiGa1-xiAs的厚度.另外,异质结的层数对声子输运也产生一定的影响.

Using a transfer matrix method, we investigate the transmission property of the acoustic-phonon modes in symmetrical multilayer heterojunctions consisting of many different heterojunctions （GaAs/Alxi Ga1-xi As ） within elastic continuum approximation. Our results show that the oscillation amplitude and frequency are different between transmission curve in such structure and transmission curve in the superlattice （GaAs/AlAs） with the same thicknesses of constituent layers. The features of transmission spectrum are influenced by the distribution of the concentration xi （ i denotes the i th Alxi, Ga1-xi, As slab on both sides of the symmetrical axis） . When the concentration xi in Alxi Ga1-xi As slab decreases with the increase of i, the curve in transmission spectrum is flat except in the vicinity of the main valley. When the concentration xi increases with the increase of i, the oscillation amplitude of the curve increases and the main valley is split. Our results also show that the transmission coefficient is sensitive to the thicknesses of constituent layers, especially the thickness of Alxi, Ga1-xi, As. In addition, it is found that the number of heterojunctions influences the transmission of acoustic phonon.