Discrepancies in the transconductance obtained from pulsed S-parameters and pulsed I-V curves of PHEMT devices

The extrinsic transconductance of a PHEMT device is examined using a rigorous isothermal pulsed I-V technique. The extrinsic transconductance is determined directly from the pulsed I-V (gm pulsed) measurements and compared with pulsed S-parameter measurements (gm RF). The discrepancy between gm pulsed and gm RF for the Vgs range of -1.0 to -0.4 is less than 10%. Transconductance extracted from the conventional DC I-V measurements (gm DC) differs by greater than 35% from the gm RF values over this same Vgs range