Characteristics of GaAs Power MESFETs with Double Silicon Ion Implantations for Wireless Communication Applications

GaAs power metal-semiconductor field-effect transistors (MESFETs) were fabricated using direct double silicon (Si) ion implantation technology for wireless communication applications. A 150-μm MESFET had a saturation drain current of 238 mA/mm after Si3N4 passivation. A 15-mm MESFET, when measured under a class-AB condition with a biased drain voltage of 3.4 V and a quiescent drain current of 600 mA, delivered a maximum output power (Pout) of 31.1 dBm and a maximum power-added efficiency (PAE) of 58.0% at a frequency of 1.88 GHz. The MESFET exhibited a Pout of 29.2 dBm with a PAE of 45.0% at the 1-dB gain compression point. The MESFET, when measured under a deep class-B condition with a biased drain voltage of 4.7 V and a quiescent drain current of 50 mA, achieved a maximum Pout of 33.1 dBm and a maximum PAE of 55.9% at 1.88 GHz. The MESFET operating at 4.7 V and 1.88 GHz exhibited a P1dB of 31.8 dBm and an associated PAE of 47.1% at the 1-dB gain compression point. When tested by IS-95 code-division multiple access (CDMA) standard signals and biased at 4.7 V under the deep class-B condition, the MESFET with a Pout of 28 dBm demonstrated an adjacent channel power rejection (ACPR) of –31.2 dBc at +1.25 MHz apart from the 1.88 GHz center frequency and –45.7 dBc at +2.25 MHz.