NON-ALLOYED AND INSITU OHMIC CONTACTS TO HIGHLY DOPED N-TYPE GAAS LAYERS GROWN BY MOLECULAR-BEAM EPITAXY (MBE) FOR FIELD-EFFECT TRANSISTORS

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.