Condensed-Matter Physics & Materials Science Seminar

The integration of semiconducting nanowires into a device requires having dielectric materials in contact with semiconducting nanowires. Therefore understanding the effect of surrounding dielectric materials on properties of semiconducting nanowires is quite relevant for the device integration of semiconducting nanowires.
In this work, we grow GaN nanowires by CVD. The nanowires are typically 20 – 50 nm in diameter and 10 – 15 m long. The TEM studies indicate good crystalline growth. The crystal growth direction is determined to be (101¯ 0) by SADP (Selected Area Diffraction Pattern). Back-gated Field Effect Transistors are fabricated using e-beam lithography and their device characteristics are measured electronically.
We present the effect of dielectric surroundings on electrical properties of gallium nitride nanowires. Two configurations are considered: bare suspended and SiO2-coated nanowires. The conductivities of n-doped gallium nitride nanowires are measured from 4.2 to 300 Kelvin. Two sets of impurity activation energies are extracted from the conductivity versus temperature measurements, indicating multichannel conduction. The larger activation energy, attributed to activation of impurities into the conduction subband, is found to display an inverse dependence on the nanowire radius. This size dependence is explained by the self-energy correction due to the image charges formed at the surface of nanowires. The smaller activation energy is independent of the nanowire radius, suggesting a surface conduction.