Nonalloyed and <i>i</i> <i>n</i> <i>s</i> <i>i</i> <i>t</i> <i>u</i> Ohmic contacts to highly doped <i>n</i>-type GaAs layers grown by molecular beam epitaxy (MBE) for field-effect transistors

Abstract

MBE was used to grow n-type GaAs layers doped with tin to approximately 5×1019 cm−3. Au/Ge Ohmic contacts were formed on the heavily doped layers without exceeding the eutectic temperature, thereby producing a nonalloyed Ohmic contact. In an in situ metallization experiment, tin was deposited on a freshly grown n++ layer. The deposited contact (without any heating) has linear current-voltage characteristics. Power GaAs FET’s were fabricated with nonalloyed Au/Ge contacts which showed excellent rf and dc characteristics. The combination of MBE n++ layer growth and the technology presented here may have potential for microwave devices and GaAs integrated circuits.