Impact of SF 6 plasma treatment on performance of AlGaN/GaN HEMT

Abstract

Selective plasma treatment of an AlGaN/GaN heterostructure in the RF discharge of the electronegative SF 6 gas was studied. Shallow recess-gate etching of AlGaN (∼5 nm) was performed in CCl 4 plasma through a photoresist mask. Subsequently, recess-gate etching followed in situ by SF 6 plasma. The plasma treatment provides the following advantages in the technology of AlGaN/GaN high-electron mobility transistors (HEMT): It (1) simplifies their technology; (2) ensures sufficient selectivity; and (3) enables the technologist to set the threshold voltage of the HEMTs controllably. At the same time, the treatment can (1) provide the AlGaN/GaN heterostructure with surface passivation; (2) modify the 2DEG in any area of a HEMT channel; and (3) make it possible to convert a HEMT operation from depletion mode to enhancement mode. The treatment also improved significantly the DC and RF parameters of HEMTs studied.