Author :
Thayne, I.G. ; Asenov, Asen ; Hill, R.J.W. ; Holland, M.C. ; Kalna, Karol ; Li, Xin ; Macintyre, D. ; Moran, D.A.J. ; Stanley, C.R. ; Thoms, S. ; Zhou, Huimin ; Abrokwah, J. ; Droopad, Ravi ; Fejes, P. ; Hartin, Olin ; Johnson, Eric ; Park, Y.-B. ; Rajago
Abstract :
This paper summarises the current state of the art in GaAs MOSFETs, and argues that the 4 decade search for a device quality compound semiconductor oxide is over. Under suitable growth conditions, a GaO/GaGdO high-k (~20) gate dielectric has been shown to have a mid-gap density of states of 2.5 x 1011 cm-2 eV-1 [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 comp25GaAs channel layer, have yielded electron transport metrics comparable to GaAs pHEMTs of similar materials compositions-namely mobility of above 5000 cm2/Vs for carrier concentration above 2 x 1012 cm-2 [4]. From these material structures, 1 mum 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,arable to GaAs pHEMTs of similar materials compositions-namely mobility of above 5000 cm2/Vs for carrier concentration above 2 x 1012 cm-2 [4]. From these material structures, 1 mum 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 = 477 mS/mm, output conductance, gd = 11 mS/mm , gate leakage current, Ig = 60 pA for gate voltages up to + 2.0 V, subthreshold swing, S = 102 mV/dec, on resistance, Ron = 1.920 Omegamm, and Ion/Ioff ratio = 6.3 x 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 transcondu- tance 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 0.8 mum gate length III-V MOSFETs with a threshold voltage of +0.4 V, resulted in fT and fmax of 14 GHz and 40 GHz respectively.
Keywords :
III-V semiconductors; MMIC; MOSFET; gadolinium compounds; gallium arsenide; high electron mobility transistors; indium compounds; GaO-GaGdO; In0.25GaAs; MOSFET; current 60 pA; frequency 14 GHz to 40 GHz; gate leakage current; high-k gate dielectric; maximum extrinsic transconductance; mid-gap density; oxide-semiconductor interface; pHEMT; peak intrinsic transconductance; quality compound semiconductor oxide device; saturation drive current; single supply III-V RF technology; size 0.8 mum; size 10 nm; size 300 nm; subthreshold swing; threshold voltage; voltage 0.26 V; voltage 2 V; GaAs MOSFETs; RF; single power supply;
