A LIGHTLY DOPED DEEP DRAIN GAAS-MESFET STRUCTURE FOR LINEAR-AMPLIFIERS OF PERSONAL HANDY-PHONE SYSTEMS

An improved GaAs MESFET structure, named a buried p-layer lightly dope d deep drain (BP-LD3) structure, is proposed, This structure can be fa bricated by the conventional self-aligned gate and selective ion impla ntation technologies, and the FET characteristics show a high transcon ductance, a high breakdown voltage, and a low drain-source resistance, The lightly doped deep drain characterizing this structure was introd uced on the basis of a two-dimensional numerical analysis including an impact ionization for a buried p-layer lightly doped drain (BP-LDD) s tructure which has been applied for high-speed digital IC's, The simul ated results clarified that a low breakdown voltage of the BP-LDD stru cture originates from a high rate of carrier generation due to the imp act ionization in the lightly doped drain region, The reason is that b oth electric field and current density become high in the region, In t he new BP-LD3 structure, the electron current deeply expands due to th e deep formation of lightly doped drain, therefore impact ionization i s reduced, This BP-LD3 structure was fabricated and the FET characteri stics were compared with those of the conventional BP-LDD structure, a nd a structure which is now being studied for linear amplifies of 1.9 GHz personal handy-phone systems, The measured breakdown voltage of 8. 1 V, transconductance of 360 mS/mm, and drain-source resistance of 2.5 Omega/mm for the BP-LD3 structure indicate high potentiality for anal og applications.