| Summary: | In this paper, we introduce novel surface treatments of UV/Ozone and TMAH to solve the surface problem of gate recess of InAlAs/InGaAs InP-based HEMTs. The problem of nonstoichiometric surface of InP etch stopper layer was found to be the result of donor-like surface defects brought by HF damage, bringing troubles like kink effect, high gate leakage current and deteriorated noise performance. Through the method of surface treatments, the InAlAs/InGaAs InP-based HEMTs exhibit excellent DC performances, demonstrating a low gate leakage currents of 10 -8 A/um, a peak transconductance of 1100mS/mm, an improved subthreshold swing of 92.5mV/decade at V<sub>ds</sub> = 1.0V, and a positive threshold voltage shift of V<sub>th</sub> = 300 mV. The ft of 260GHz and fmax of 440GHz were hardly influenced by the surface treatments while the noise performances were improved obviously. Two orders of magnitude smaller input noise spectral density shows the method of surface treatment can effectively reduce the surface defects and significantly improve the surface of gate recess of InAlAs/InGaAs InP-based HEMTs.
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