A DOUBLE LIGHTLY DOPED DRAIN (D-LDD) STRUCTURE H-MESFET FOR MMIC APPLICATIONS

This paper proposes a new double lightly doped drain (D-LDD) structure for InGaP/InGaAs heterostructure MESFET's (H-MESFET's). A D-LDD H-MES FET has three kinds of low-resistant layers in the drain region, while a conventional LDD H-MESFET has two layers, This structure improves m aximum stable gain (MSG) accompanied by R-d reduction with minimized g ate-breakdown-voltage degradation and C-gd increase, A heuristic model is proposed to predict V-bgd from sheet resistance of implanted layer s, and its validity is confirmed with experimental data, This model su ccessfully predicted the tradeoff relation between V-bgd and parasitic resistance, and it has enough generality so that it can be applied to usual ion-implanted GaAs MESFET's, Consequently, a typical MSG at 50 GHz exhibits 8.9 dB in a MESFET and 7.7 dB S21 in an one-stage amplifi er, The high-frequency circuit operation proves that this technology i s one of the most promising for monolithic-microwave integrated-circui t (MMIC) applications.