Study of surface-trap-induced gate depletion region of field-modulating plate GaAs–FETs

To investigate the cause of the superior RF output power performance of GaAs–FETs with a field-modulating plate, the impact of a field-modulating plate on the surface-trap-induced gate depletion region is evaluated using pulsed I–V characteristics of GaAs–FETs with and without a field-modulating plate. In conventional FETs (without a field-modulating plate), the very high density of the trapped electrons (∼1012 cm−2), which are localized at the gate edge on the drain side, generates a surface depletion region extending deeply in the vertical direction. In FETs with a field-modulating plate, on the other hand, this detrimental phenomenon is significantly suppressed. Finally, this investigation shows that both RF saturated output power measured and that calculated using pulsed I–V characteristics are reasonably consistent.