%0 Journal Article
%T Germanium Doping to Improve Carrier Mobility in CdO Films
%A A. A. Dakhel
%J Advances in OptoElectronics
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/804646
%X This investigation addresses the structural, optical, and electrical properties of germanium incorporated cadmium oxide (CdOˋ:ˋGe) thin films. The focus was on the improvement in carrier mobility to achieve high transparency for near-infrared light and low resistivity at the same time. The properties were studied using X-ray diffraction, SEM, spectral photometry, and Hall measurements. All CdOˋ:ˋGe films were polycrystalline with high texture orientation along [111] direction. It was observed that it is possible to control the carrier concentration ( ) and mobility ( ) with Ge-incorporation level. The mobility could be improved to a highest value of ˋcm2/V﹞s with Ge doping of 0.25ˋwt% while maintaining the electrical resistivity as low as ˋ次﹞cm and good transparency % in the NIR spectral region. The results of the present work proved to select Ge as dopant to achieve high carrier mobility with low resistivity for application in transparent conducting oxide (TCO) field. Generally, the properties found make CdOˋ:ˋGe films particularly interesting for the application in optoelectronic devices like thin-film solar cells. 1. Introduction Transparent conduction oxides (TCOs) like ZnO, CdO, SnO2, In2O3, and NiO are degenerate semiconducting group. They exhibit typical n-type conduction, which is caused by a deviation from stoichiometry due to the low formation energies for intrinsic donor defects, such as natural structural metal interstitials (Mi) and oxygen vacancies (VO). It was found that it is possible to control TCO optoelectronic properties by managing and controlling their structural defects. Therefore, the TCOs have widespread use in many advanced technologies, like flat panel displays and solar energy systems [1]. Therefore, it is necessary to examine ways for improving their optoelectronic functions. These enhancements could be realized by a suitable doping, which increases the carrier mobility ( ) and consequently the conductivity but without reduction in the transparency. The present work deals with CdO. It is one of TCOs with an n-type electrical resistivity of 10ˋ2每10ˋ4ˋ次﹞cm and good transparency in the visible and NIR spectral regions with a direct bandgap of 2.2每2.7ˋeV [2每4]. The carrier mobility in CdO films is considerably dependent on growth method and conditions, like the type of the substrate and its temperature. For example, the room-temperature carrier mobility in CdO film grown by MOCVD method on glass substrate at 412∼C was 105ˋcm2/V﹞s [5]. This high mobility was attributed to a reduction in neutral impurity scattering (NIS) due to
%U http://www.hindawi.com/journals/aoe/2013/804646/