Effects of Surface Passivation and Deposition Methods on the 1/<inline-formula> <tex-math notation="LaTeX">$f$ </tex-math></inline-formula> Noise Performance of AlInN/AlN/GaN High Electron Mobility Transistors

Abstract

This letter reports on effects of Si3N4 and Al2O3 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 Al2O3, deposited by two different methods: 1) thermal atomic layer deposition (ALD) and 2) plasma-assisted ALD. The third sample is passivated with Si3N4 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 Al2O3 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 Al2O3, is a good candidate for millimeter-wave power generation.