Investigation of DC-RF and breakdown behaviour in Lg = 20 nm novel asymmetric GaAs MHEMTs for future submillimetre wave applications

In this work, we systematically investigated the DC-RF and breakdown voltage characteristics of Lg = 20 nm novel asymmetric GaAs metamorphic high electron mobility transistor (MHEMT) using Sentaurus-TCAD tool. The highlights of the novel asymmetric GaAs MHEMT are the cavity in the asymmetric Γ-gate region, n+-type In0.52Al0.48As/In0.53Ga0.47As/In0.75Ga0.25As cap layers and n+-type In0.52Ga0.48As vertical source/drain (S/D) regions. The influence of asymmetric gate recess width on DC-RF and ON and OFF-state breakdown voltage characteristics of the novel asymmetric GaAs MHEMT has been systematically investigated using hydrodynamic (HD) charge transport model. The physical models such as impact ionization model, high electric field electron mobility model, Shockley-Read-Hall and recombination models and density gradient model are also included during room temperature Sentaurus-TCAD simulation in order to accurately obtain the DC-RF and breakdown performance parameters. The 20 nm gate length novel asymmetric GaAs MHEMT obtained a maximum transconductance (gm_max) and drain current IDS_max of 3350 mS/mm and 1230 mA/mm respectively. The transit frequiencies fT and fmax obtained by the proposed 20 nm gate length GaAs MHEMT are 643 GHz and 1230 GHz respectively. The 20 nm gate length novel asymmetric GaAs MHEMT also exhibited an ON-state (BVON) and OFF-state (BVOFF) breakdown voltages of 3.1 V and 7.2 V respectively. To the best knowledge of authors, this is the record combination of DC-RF and breakdown performance parameter values obtained for GaAs MHEMT which makes them highly suitable for next generation high power high speed applications.