K. Nishihori et al., A SELF-ALIGNED GATE GAAS-MESFET WITH P-POCKET LAYERS FOR HIGH-EFFICIENCY LINEAR POWER-AMPLIFIERS, I.E.E.E. transactions on electron devices, 45(7), 1998, pp. 1385-1392
This paper describes a newly developed GaAs metal semiconductor field-
effect transistor (MESFET)-termed p-pocket MESFET-for use as a linear
power amplifier in personal handy-phone systems. Conventional buried p
-layer technology, the primary technology for microwave GaAs power MES
FET's, has a drawback of low power efficiency for linear power applica
tions. The low power efficiency of the buried p-lager MESFET is ascrib
ed to the I-V kink which is caused by holes collected in the buried p-
layer under the channel. In order to overcome this problem, we have de
veloped the self-aligned gate p-pocket MESFET which incorporates p-lay
ers not under the channel but under the source and drain regions. This
new MESFET exhibited high transconductance and uniform threshold volt
age. The problematic I-V kink was successfully removed and an improved
power efficiency of 48% was achieved under bias conditions, which res
ulted in adjacent channel leakage power at 600-kHz offset as low as -5
9 dBc for 1.9-GHz pi/4-shift QPSK modulated input.