Turning the n-Type CdS to p-Type CdS Nanowires By Surface Charge Transfer Doping

Abstract

One-dimensional semiconductor nanostructure has been attracted great attention in electronic and optoelectronic applications in recent years. N-type CdS nanowires (NWs) doped with gallium were synthesized via chemical vapor deposition method[ 1 ]. In contrast to have n-type doping for CdS, p-type doping is relatively difficult to achieve due to the strong self-compensation [ 2,3 ]. In this work, we emonstrated the p-type doping of CdS NWs can be achieved by coating ~ 100 nm MoO3 onto CdS surface. Owing to the large work function of MoO3, the electrons in CdS are transfer to MoO3 and CdS exhibits the p-type characteristics, this process is called surface charge transfer doping. The charge transfer process was analyzed by X-ray photoelectron spectroscopy. MoO3-coated CdS NWs were then confirmed to be p-type by the back-gate field-effect transistors (FETs). Fig. 1(a) shows the optical microscopy image of back-gate Ga-doped CdS NW FET device. Fig. 1(b) depicts drain current (Id) versus drain voltage (Vd) at gate voltages (Vg) ranging from -30 V to 30 V at room temperature, it reveals typical n-type behavior. Besides, the transfer characteristic curves (Id-Vg) of Ga-doped CdS NW and MoO3-coated CdS NW devices shown in Fig. 1(c) as black and red curves, respectively. It is obvious that Ga-doped CdS NW reveals p-type characteristic after MoO3 layer coating. Finally, the MoO3-coated CdS/CdS NW junction photovoltaic devices were fabricated and discussed. Reference Cai, Jiajun et al., Phys. Chem. Chem. Phys., 13, 14663-14667, 2011Xie, Chao et al., J. Mater. Chem. C, 3, 6307-6313, 2015Li, Fang-Ze et al., Adv. Energy Mater., 3, 579-583, 2013 Figure 1