High mobility GaAs layers obtained by open tube sulfur diffusion

摘要

A new technique to diffuse sulfur in GaAs has been demonstrated. The diffusion is performed on a 2hyphen;in. liquid encapsulated Czochralski GaAs wafer in an open tube furnace under N2flow. A graphite assembly is used to keep the diffusion source and the wafer in close proximity. Diffusion at 850thinsp;deg;C for 30 min gave a sheet carrier concentration of 8.2times;1012cmminus;2, average mobility of 4200 cm2/Vthinsp;s, and sheet resistance of 180 OHgr;/laplac;. Sheet resistance uniformity is about plusmn;5percnt;. Transconductances as high as 200 mS/mm have been measured on metalhyphen;semiconductor fieldhyphen;effect transistors with 2 mgr;m gate length, fabricated on layers diffused by this technique.