We present a fully analytical model and physical investigation on the source resistance (R_S) in In_xGa_1−xAs quantum-well high-electron mobility transistors based on a three-layer TLM system. The R_S model in this work was derived by solving the coupled quadratic differential equations for each current component with appropriate boundary conditions, requiring only six physical and geometrical parameters, including ohmic contact resistivity (ρ_c), barrier tunneling resistivity (ρ_barrier), sheet resistances of the cap and channel regions (R_{sh_cap} and R_{sh_ch}), side-recessed length (L_side) and gate-to-source length (L_gs). To extract each model parameter, we fabricated two different TLM structures, such as cap-TLM and recessed-TLM. The developed R_S model in this work was in excellent agreement with the R_S values measured from the two TLM devices and previously reported short-L_g HEMT devices. The findings in this work revealed that barrier tunneling resistivity already played a critical role in reducing the value of R_S in state-of-the-art HEMTs. Unless the barrier tunneling resistivity is reduced considerably, innovative engineering on the ohmic contact characteristics and gate-to-source spacing would only marginally improve the device performance.

In this paper, we report the fabrication and characterization of L_g = 50 nm Gate-All-Around (GAA) In_0.53Ga_0.47As nanosheet (NS) metal-oxide-semiconductor field-effect transistors (MOSFETs) with sub-20 nm nanosheet thickness that were fabricated through an S/D regrowth process. The fabricated GAA In_0.53Ga_0.47As NS MOSFETs feature a bi-layer high-k dielectric layer of Al₂O₃/HfO₂, together with an ALD-grown TiN metal-gate in a cross-coupled manner. The device with L_g = 50 nm, W_NS = 200 nm and t_NS = 10 nm exhibited an excellent combination of subthreshold-swing behavior (S < 80 mV/dec.) and carrier transport properties (g_{m_max} = 1.86 mS/μm and I_ON = 0.4 mA/μm) at V_DS = 0.5 V. To the best of our knowledge, this is the first demonstration of In_xGa_1-xAs GAA NS MOSFETs that would be directly applicable for their use in future multi-bridged channel (MBC) devices.