Space charge limited currents and trap concentrations in GaAs nanowires

Electrical transport through individual solution-grown GaAs nanowires was measured as a function of temperature. The current-voltage (IV) curves are nonlinear and exhibit space charge limited currents. The IV curves become increasingly nonlinear with decreasing temperature and follow the scaling relationship J proportional to Vl+1. This scaling indicates that the space charge limited currents are limited by trapped charge. The characteristic energies of the trap states were estimated from the IV data and found to vary from wire to wire, ranging from 0.024 to 0.11 eV below the band edge. In the low bias region of the IV curves, where the curves were ohmic, the activation energy (related to the Fermi energy) was determined and found to be shifted significantly towards the band edge, which indicates either the presence of a large concentration of impurities, such as Si, in the nanowires or charged surface states.