Experimental and theoretical investigation of parameter evolution of ultra-short gate standard and pseudomorphic HEMTs

We present a coordinated experimental and theoretical investigation of the parameter evolution of ultra-short gate HEMTs down to 0.1¿m gate-length, and of the physical and electrical limitations to performance improvements. The study encompasses a broad range of well qualified situations allowing comparisons with previous investigations[1-4]. The main features are,- the exploitation of two reliable technological processes namely planar-doped double- recessed AlGaAs/GaAs HEMT (S-HEMT) and planar-doped pseudomorphic AlGaAs/GaInAs/GaAs HEMT with T-shaped and rectangular gate (PM-HEMT), represented in Fig. 1 and 2), - coherent evolutions of full electrical parameter extractions from dc and 0.1- 40GHz HF coplanar probe on-chip measurements, including capacitances versus gate length down to 0.1¿m, - physical modeling based on a quasibidimensional hydrodynamic approach (Q-2D), allowing systematic parametrisation of HEMTs, completed with electromagnetic finite element 2-D modeling of electrostatic parasitic capacitances, - physical modeling based on Monte Carlo simulations (MC) for the investigation of short lg transistors. For the gate width lg¿0,1 ¿m this analysis shows that the optimization of S- and PM-HEMT depends on three parameters: - a weak influence of Vds on the diffusion under the gate, - a low parasitic electrostatic capacitance, - a high carrier velocity.