CONTROLLING THE ELECTRICAL PROPERTIES OF GUIDED GaN NANOWIRES

Semiconductor nanowires (NWs) are important materials, found today in the basis of many potential nanotechnological applications and scientific research. Recently, our group has reported a new approach for the guided growth of aligned horizontal GaN, ZnO and ZnSe NWs on different substrates, via the vapor-liquid-solid (VLS) mechanism. This new method enables control over the NWs location, growth direction and crystallographic orientation, and can lead to specific design of nanodevices. GaN specifically is an important semiconductor having a wide direct band-gap of 3.4 eV (UV), suitable for different electronic and optoelectronic applications. GaN NWs are unintentionally n- doped due to nitrogen vacancies and/or oxygen impurities, which often causes a high concentration of charge carriers. This often reduces their field-effect mobility, affecting the performance of nanowire-based transistors. Here we demonstrate the control of the unintentional-doping level, using alumimium as an oxygen getter agent in the synthesis of GaN NWs. In the chemical vapor deposition (CVD) system, the alumimium precursor can react with the oxygen in the reactor, originating from the Ga₂O₃ precursor and impurities in the system. This can possibly allow the growth of GaN NWs with less oxygen impurities in the lattice, bringing down the n-doping level. The guided NWs were examined in different compositional analysis methods (EELS spectroscopy, EDS and photoluminescence), which showed that the aluminium is not incorporated in the NW lattice (less than 2%). Electrical measurements show higher resistivity for GaN NWs grown with aluminium, and much higher response to gating. These findings can indicate that the aluminium acts as an oxygen getter agent during the synthesis. This gettering method is shown to enable control of the electrical properties of guided NWs.