Investigation of AlGaN/GaN fluorine plasma treatment enhancement-mode high electronic mobility transistors by frequency-dependent capacitance and conductance analysis

This paper reports fluorine plasma treatment enhancement-mode HEMTs (high electronic mobility transistors) EHEMTs and conventional depletion-mode HEMTs DHEMTs fabricated on one wafer using separate litho-photography technology.It finds that fluorine plasma etches the AlGaN at a slow rate by capacitance-voltage measurement.Using capacitance-frequency measurement,it finds one type of trap in conventional DHEMTs with τ T=(0.5 6) ms and D T=(1 5)×10 13 cm 2 · eV 1.Two types of trap are found in fluorine plasma treatment EHEMTs,fast with τ T(f)=(0.2 2) μs and slow with τ T(s)=(0.5 6) ms.The density of trap states evaluated on the EHEMTs is D T(f)=(1 3) × 10 12 cm 2 · eV 1 and D T(s)=(2 6) × 10 12 cm 2 · eV 1 for the fast and slow traps,respectively.The result shows that the fluorine plasma treatment reduces the slow trap density by about one order,but introduces a new type of fast trap.The slow trap is suggested to be a surface trap,related to the gate leakage current.