A SELF-ALIGNED GATE ALGAAS GAAS HETEROSTRUCTURE FIELD-EFFECT TRANSISTOR WITH AN ION-IMPLANTED BURIED-CHANNEL FOR USE IN HIGH-EFFICIENCY POWER-AMPLIFIERS/

In this paper we report on a self-aligned gate buried-channel Al0.22Ga 0.78As/GaAs heterostructure field-effect transistor (BC-HFET). The BC- HFET comprises a selectively ion-implanted channel and an undoped i-Al GaAs surface layer. In order to realize the buried channel heterostruc ture, a combined process of ion-implantation and epitaxial growth is d eveloped. The postimplantation annealing before the epitaxial growth s uccessfully reduces the interdiffusion at the heterointerface between the ion-implanted GaAs channel and the AlGaAs surface layer. The BC-HF ET overcomes the disadvantages of a low breakdown voltage which exists in conventional self-aligned gate MESFETs. The BC-HFET exhibits a hig h breakdown voltage of 8 V and a high Schottky barrier height of 0.75 eV. The l-mm-wide power BC-HFET demonstrates an output power of 18.2 d Bm and a drain efficiency of 50% at a low adjacent channel leakage pow er of -59 dBc for a 1.9-GHz pi/4-shifted quadrature phase shift keying (QPSK) modulated input, for use as Personal Handy-phone System handse ts.