Wednesday, March 11, 2015

Chalmers and Thales reduce low-frequency noise in AlInN/GaN HEMTs by ALD/PEALD passivation

As reported by Semiconductor Today, researchers based in Sweden* and France** have been exploring various passivations for reducing low-frequency noise (LFN) in gallium nitride (GaN) high-electron-mobility transistors (HEMTs) with aluminium indium nitride (AlInN) barriers [Thanh NgocThi Do etal, IEEE Electron Device Letters, published online 6 February 2015]. The researchers claim that one of their passivation processes produced the best reported LFN for AlInN/GaNHEMTs.
Effects of surface passivation and deposition methods on the 1/f noise performance of AlInN/AlN/GaN HEMTs

Do, T., Malmros, A. ; Horberg, M. ; Rorsman, N. ; Kuylenstierna, D. ; Gamarra, P. ; Lacam, C. ; Poisson, M. ; Tordjman, M. ; Aubry, R.

Electron Device Letters, IEEE  (Volume:PP ,  Issue: 99 )

This paper 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: thermal Atomic Layer Deposition (ALD) and plasma-assisted ALD. The third sample is passivated with Si3N4 using Plasma-Enhanced Chemical Vapor Deposition (PECVD). 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 10kHz is 1×10-14 Hz-1 for a bias of Vdd/Idd = 10V/80mA. To the authors’ best 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 millimetre-wave power generation. 
Figure 1: Drain noise current spectra of the three AlInN/AlN/GaN HEMTs versus frequency at 10V, 17mA operating point.

Drain noise current spectra of the three AlInN/AlN/GaN HEMTs versus frequency at 10V, 17mA operating point. (Semiconductor Today, Electron Device Letters, IEEE  (Volume:PP ,  Issue: 99 ) )
* Microwave Electronics Laboratory, Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, , Sweden
** The Wide Band Gap Materials Laboratory and the GaN process Laboratory of 3-5 Lab/Thales Research & Technology, Marcoussi, France