High-transconductance p-channel AlGaAs/GaAs HFETs with low-energy beryllium and fluorine co-implantation self-alignment

Abstract
The fabrication and electrical characteristics of p-channel AlGaAs/GaAs heterostructure FETs with self-aligned p/sup +/ source-drain regions formed by low-energy co-implantation of Be and F are reported. The devices utilize a sidewall-assisted refractory gate process and are fabricated on an undoped AlGaAs/GaAs heterostructure grown by MOVPE. Compared with Be implantation alone, the co-implantation of F/sup +/ at 8 keV with 2*10/sup 14/ ions/cm/sup 2/ results in a 3* increase in the post-anneal Be concentration near the surface for a Be/sup +/ implantation at 15 keV with 4*10/sup 14/ ions/cm/sup 2/. Co-implantation permits a low source resistance to be obtained with shallow p/sup +/ source-drain regions. Although short-channel effects must be further reduced at small gate lengths, the electrical characteristics are otherwise excellent and show a 77-K transconductance as high as 207 mS/mm for a 0.5- mu m gate length.