Controlled device parameters of high-mobility polymer field-effect transistors (FETs) are demonstrated by modest doping and charge compensation. Through fleeting chemical vapor treatments of aligned poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b: 5,4-b'] dithiophen-2-yl)alt-[1,2,5] thiadiazolo-[3,4-c] pyridine] (PCDTPT) thin films as the charge transport layer in the FET channel, the FET properties are tailored by controlling doping concentration of the PCDTPT adjacent to metal electrodes.