Acoustically driven charge separation in semiconductor heterostructures sensed by optical spectroscopy techniques

Abstract

Abstract:We demonstrate a method of using a two-layer sandwich structure, which includes a LiNbO 3 plate and a semiconductor heterostructure to create an inhomogeneous stress and piezoelectric harmonic potential in the semiconductor. Both the GaAs/AlGaAs quantum well (QW) structures and SiGe/Si heterostructures are attempted, working with and without using a piezoelectric field in the semiconductor layer. The standing-wave fields generated in the semiconductor and the electron and hole distributions driven by the piezoelectric field are computed by finite element method (FEM) techniques. It is experimentally shown that, in a GaAs/Al Ga 1− As asymmetric double quantum well structure, the resonance enhancement of the narrower QW photoluminescence band is observed, which may be explained by the resonant charge transfer between the wider and narrower QWs. It is also shown that the piezoelectric fields quench the pure LO-phonon lines in the Raman spectra, whereas the coupled LO-phonon-plasmon mode strengthens. Experimental results indicate that the charge separation occurs in the plane of the QWs due to the piezoelectric fields. The recombination of carriers in the SiGe/Si heterostructures can be effectively enhanced by the presence of ultrasonic stress, displaying features consistent with varying electrical activity at dislocations. 78.67.De, 78.20.Hp, 62.65.+k PACS (2008):

Electrochemical Growth and Structural Study of the AlxGa1−xAs Nanowhisker Layer on the GaAs Surface

“…For the Al x Ga 1−x As material, typical Raman scattering peaks are generally between 260-290 cm −1 and 360-390 cm −1 [55]. The relative positions of the peaks depend on the structural organization of the alloy and the content of Al.…”