AN AFM-BASED SURFACE OXIDATION PROCESS FOR HEAVILY CARBON-DOPED P-TYPE GAAS WITH A HOLE CONCENTRATION OF 1.5 X 10(21) CM(-3)

Under appropriate bias conditions in ambient humidity, AFM can be used to selectively oxidize the surface of electronic materials such as me tals and semiconductors. Therefore, an AFM-based surface modification technique would be a powerful tool for fabricating nanometer-sized met al (M)/insulator (I) or semiconductor (S)/insulator (I) junction struc tures. Heavily carbon-doped p-type GaAs with a hole concentration of 1 .5 x 10(21) cm(-3) is also of great interest for application to novel device structures, because the carrier concentration is comparable to that of normal metals. Selective surface oxidation of carbon-doped p-t ype GaAs was achieved using a negatively biased conductive tip. The ox idation shown here was carried out under 20-25% ambient humidity. By c hanging the applied bias voltage and the scanning speed of the cantile ver, the size of the modified structure wires was precisely controlled , with a feature size of similar to 10 nm. These results suggest that GaAs-based devices with ultra-small SIS junction systems could be real ized using the AFM-based surface oxidation process.