Study of hot electron effect in sub-micron semiconductor devices.

超热电子的动力学性质对亚微米半导体器件的性能有很大的影响。在化合物半导体器件中，电子-极性光学声子相互作用主导散射现象。在本项目中，我们研究了异质结构和超晶格中超热电子与电离杂质和极性光学声子相互作用的量子尺寸效应，数值研究了异质结构和超晶格的晶格动力学，发现层状结构对光学模有很强的影响，这些光学模局限于层内，而声学模式仅受到轻微的修改。我们提出了电子-局域光学声子相互作用的计算公式，并据此研究了电子-声子相互作用与阱宽的关系，结果表明：量子阱越窄，极化子的弛豫时间越长，结合能越小。研究了GaAs/AlGaAs双量子阱超晶格的光致发光光谱，发现二维系统中的相互作用比三维系统中的相互作用更具有短程性质。在低温下，样品经受平行于异质界面施加的电场。通过研究光谱随电场和电子温度的变化，首次证实了电子-杂质或电子-声子相互作用引起的真实的空间转移或子带间跃迁.

The performance of a submicron semiconductor device is strongly affected by the dynamical properties of hot electrons in such a short time scale as a pico second. In a compound semiconductor device, the electron-polar optical phonon interaction predominates the scattering phenomena. In this project, we have studied the quantum size effect on the interaction of hot electrons with ionized impurities and the polar optical phonons in hetero-structures and/or superlattices.We studied numerically the lattice dynamics of hetero-structures and/or superlattices and found that the layered structure does have a strong influence on the optical modes, which are localized within the layers, while the acoustical mode suffers only a slight modification. We proposed a formula for the interaction of electron-localized optical phonons.According to the results mentioned above, the well width dependence of the electron-phonon interaction was studied, and it was shown that the narrower the quantum well is, the longer becomes the relaxation time and the smaller is the binding energy of polarons. The interaction in 2-dimensional system is shown to become more of the short range nature in comparison with the 3-dimensional one.The photo-luminescence spectra of double quantum well superlattice made of GaAs/AlGaAs system was studied. The sample was subjected to the electric field applied parallel to the hetero-interface at cryogenic temperatures. By investigating the variation of the spectra as a function of the electric field as well as the electron temperature, the real space transfer or the inter-sub-band transition via the electron-impurity or the electron-phonon interaction was confirmed for the first time.