  Gas sensors at low operating temperature with high sensitivity are the demand
for the group III nitrides owing to their high chemical and thermal stability.
The CH4 sensing is realized for the Al0.07Ga0.93N nanowires (NWs) with an
improved response over the GaN NWs at a low operating temperature of 50
{\deg}C, for the first time. Al0.07Ga0.93N NWs were synthesized via ion beam
mixing process using inert gas ion irradiation on the bilayer of Al/GaN NWs.
The sensing mechanism is explained with the help of native defects present in
the system. The number of shallow acceptors created by Ga vacancy (V_Ga) is
found to be higher in Al0.07Ga0.93N NWs than those in the as-grown GaN NWs. The
role of O antisite defect (ON) for the formation of shallow V_Ga is inferred
from photoluminescence spectroscopic analysis. These native defects strongly
influence the gas sensing behaviour resulting in the enhanced and low
temperature CH4 sensing.
