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The electronic properties of delta-doped In0.22Ga0.78As/GaAs quantum wells (QWs) are studied by van der Pauw Hall measurements and Shubnikov-de Haas measurements. From the temperature-dependent van der Pauw Hall measurements, two kinds of donors are observed, which have binding energies of 104 (plusmn) 7 and 9.6 (plusmn) 0.1 MeV.

Abstract: In this research, dye-sensitized solar cells based on TiO2 micro-pillars fabricated by inductive couple plasma etcher were investigated by analyses of X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, ultraviolet-visible absorption spectra (UV–vis), and current–voltage characteristics. X-ray diffraction patterns show that the TiO2 anatase phase forms while sintering at 450°C for 30min. The SEM images reveal that the diameter and height of TiO2 micro-pillars are about 3 and 0.8μm, respectively. The measurements of contact angle between TiO2 micro-pillars and deionized water (DI water) reveal that the TiO2 micro-pillars is super-hydrophilic while annealed at 450°C for 30min.The absorption spectrum of TiO2 micro-pillars is better than TiO2 thin film and can be widely improved in visible region with N3 dye adsorbed. The results of current–voltage (I–V) characteristics analysis reveal that dye-sensitized solar cell with TiO2 micro-pillars electrode has better I–V characteristics and efficiency than TiO2 film electrodes. This result may be due to the annealed TiO2 micro-pillars applied on the electrode of dye-sensitized solar cell can increase the contact area between TiO2 and dye, resulting in the enhancement of I–V characteristics and efficiency for dye-sensitized solar cell. [Copyright &y& Elsevier]