Characteristics of δ-doped InAlAs/InGaAs/InP high electron mobility transistors with a linearly graded In_xGa_1-xAs channel

Various static and microwave performances on InAlAs/InGaAs/InP HEMTs with a linearly-graded In_xGa_1-xAs channel (LGC-HEMT) have been comprehensively investigated and compared to those having a conventional lattice-matched In_0.53Ga_0.47As channel (LM-HEMT). Improved carrier transport characteristics and confinement capability by employing the linearly-graded channel have contributed to superior extrinsic transconductance (g_m) of 346 mS mm^-1, gate-voltage swing (GVS) of 0.5 V (182 mA), unity-gain cut-off frequency (f_t) of 41 GHz and maximum oscillation frequency (f_max) of 63 GHz, with an improved frequency operation plateau at 300 K for a gate dimension of 0.65 × 200 νm². Furthermore, improved kink effects leading to a lower gate leakage current of 0.7 νA mm^-1, lower output conductance (g _d) of 3.6 mS mm^-1, higher voltage gain (A_V) of 93.1, higher off-state breakdown voltage of 16.3 V and superior output power characteristics have also been discussed.