Effects of Surface Passivation and Deposition Methods on the 1/ $f$ Noise Performance of AlInN/AlN/GaN High Electron Mobility Transistors

This letter reports on effects of Si 3 N 4 and Al 2 O 3 surface passivation as well as different deposition methods on the low-frequency noise (LFN) characteristics for AlInN/AlN/GaN high electron mobility transistors (HEMTs). Two samples are passivated with Al 2 O 3 , deposited by two different methods: 1) thermal atomic layer deposition (ALD) and 2) plasma-assisted ALD. The third sample is passivated with Si 3 N 4 using plasma-enhanced chemical vapor deposition. The LFN of the three samples is measured under a bias condition relevant for amplifier and oscillator applications. It is found that the surface passivation has a major impact on the noise level. The best surface passivation, with respect to LFN, is the thermal ALD Al 2 O 3 for which the noise current spectral density measured at 10 kHz is $1\times 10^{-14}$ Hz $^{-1}$ for a bias of $ {V}_{\rm {dd}}$ / $ {I}_{\rm {dd }} = 10$ V/80 mA. To the best of our knowledge, this result sets a standard as the best reported LFN of AlInN/GaN HEMTs. It is also in the same order as good commercial AlGaN/GaN HEMTs reported in literature and thus demonstrates that AlInN/GaN HEMTs, passivated with thermal ALD Al 2 O 3 , is a good candidate for millimeter-wave power generation.