Ultra violet (UV) light assisted residual gas desorption was performed on silicon gated field emitter array (Si-GFEAs) with 1000×1000 tips. These GFEAs can be used as vacuum nano-transistors. Here, Si-GFEAs with tips are studied experimentally in normal condition as well as under ultra-violet (UV) light exposure for a period of 100 minutes with a time step of 20 minutes. After the experiment, it was found that UV exposure enhanced the field emission current by tenfold and decreased the gate to emitter leakage by greater than ten times. This enhancement can be attributed to the residual gas desorption (water) stimulated by UV exposure, thus reducing the gate surface leakage as well as the work function of emitter tips.