Device linearity improvement and current enhancement utilizing high-to-low doping-channel FETs

Abstract

We report device linearity improvement and current enhancement in both a heterostructure FET (HFET) and a camel-gate FET (CAMFET) using InGaAs/GaAs high-low and GaAs high-medium-low doped channels, respectively. In an HFET, a low doped GaAs layer was employed to build an excellent Schottky contact. In a GaAs CAMFET, a low doped layer together with n +and p +layers formed a high-performance majority camel-diode gate. Both exhibit high effective potential barriers of >1.0 V and gate-to-drain breakdown voltages of >20.0 V (at I g =1.0 mA mm −1). A thin, high doped channel was used to enhance current drivability and to improve the transconductance linearity. A 2×100 μm 2HFET had a peak transconductance of 230 mS mm −1and a current density greater than 800 mA mm −1. The device had a transconductance of more than 80 percent of the peak value over a wide drain current range of 200 to 800 mA mm −1. A 1.5×100 μm 2CAMFET had a peak transconductance of 220 mS mm −1and a current density greater than 800 mA mm −1. Similarly, the device had a transconductance of more than 80 percent of the peak value over a wide drain current range of 160 to 800 mA mm −1. The improvement of device linearity and the enhancement of current density suggest that high-to-low doped-channel devices for both an HFET and a CAMFET are suitable for high-power large signal circuit applications.