Space charge limited conduction mechanism in GaAsSb nanowire and effect of in-situ annealing in ultra-high vacuum

In this work, the first observation of the space charge limited conduction mechanism (SCLC) inGaAsSb nanowires (NWs) grown by Ga-assisted molecular beam epitaxial technique, and theeffect of ultra-high vacuum in situ annealing have been investigated. The low onset voltage ofthe SCLC in the NW configuration has been advantageously exploited to extract trap density andtrap distribution in the bandgap of this material system, using simple temperature dependentcurrent–voltage measurements in both the ensemble and single nanowires. In situ annealing inultra-high vacuum revealed significant reduction in the trap density from 1016 cm−3 in as-grownNWs to a low level of 7×1014 cm−3 and confining wider trap distribution to a single trap depthat 0.12 eV. A comparison of current conduction mechanism in the respective single nanowiresusing conductive atomic force microscopy (C-AFM) further confirms the SCLC mechanismidentified in GaAsSb ensemble device to be intrinsic. Higher current observed in currentmapping by C-AFM, increased 4 K photoluminescence (PL) intensity along with reduced fullwidthhalf maxima and more symmetric PL spectra, and reduced asymmetrical broadening withincreased TO/LO mode in room temperature Raman spectra for in situ annealed NWs againattest to effective annihilation of traps leading to the improved optical quality of NWs comparedto as-grown NWs. Hence, the I–V–T analysis of the SCLC mechanism has been demonstrated asa simple approach to obtain information on growth induced traps in the NWs.