An investigation of cleaning procedures prior to metal gate evaporation in MESFET fabrication was undertaken. A photoresist residue was found to exist after development when using the lift‐off technique to define the gate metal pattern. This carbon residue was identified by AES depth profile measurements. Schottky diode electrical characteristics were observed to deteriorate due to this residue. Of the cleaning solutions examined, only the solution removed both C and O layers on the surface while still being compatible with the fabrication process. The effects of DI rinse time on Schottky diode electrical performance were also examined.