GaAs MOSFETs - a viable single supply III-V RF technology solution ?

This presentation will summarise the current state of the art in GaAs MOSFETs, and argue that the 4 decade search for a device quality compound semiconductor oxide is over. Under suitable growth conditions, a GaO/GaGdO high-?? (~20) gate dielectric has been shown to have a mid-gap density of states of 3??10¹¹ cm^-2[1], and vitally, an unpinned oxide-semiconductor interface [2]. With a scalable vertical architecture, enhancement mode implant-free III-V MOSFETs [3] with an In0.25GaAs channel layer, have yielded electron transport metrics comparable to pHEMTs of similar materials compositions - namely mobility of above 5000 cm²/Vs for carrier concentration above 2??10¹² cm^-2 [4]. From these material structures, 1 ??m gate length GaAs MOSFETs with a 10 nm gate oxide have been realised with threshold voltage of +0.26 V, saturation drive current, Id,sat = 407 mA/mm, maximum extrinsic transconductance, gm = 477mS/mm (the highest reported to date for a III-V MOSFET), output conductance, gd = 11 mS/mm, gate leakage current, Ig = 60 pA for gate voltages up to + 2.0V, subthreshold swing, S = 102 mV/dec, on resistance, Ron = 1.920 ??mm, and Ion/Ioff ratio = 6.3??10⁴ [4]. A gate voltage swing of +2 V can easily be accommodated with these devices, making them attractive as a single supply III-V technology. Enhancement mode operation can be sustained to 300 nm with this oxide thickness, with peak intrinsic transconductance increasing to 600 mS/mm, indicative of the on-set of non-equilibrium transport effects, similar to short gate length pHEMTs [5]. Initial RF data from 0.