Conference Paper

Effect of passivation on AlGaN/GaN HEMT device performance

Sch. of Electr. Eng., Cornell Univ., Ithaca, NY
DOI: 10.1109/ISCS.2000.947182 Conference: Compound Semiconductors, 2000 IEEE International Symposium on
Source: IEEE Xplore

ABSTRACT AlGaN/GaN HEMTs are suitable for high power applications because
of their high breakdown voltages and high currents. However, the large
signal performance of these devices is not as good as one would expect
from the DC performance of the device. The large signal performance of
the device is improved by depositing a thin layer of SiN by PECVD. In
this work silicon nitride (SiN) was deposited in a variety of conditions
on AlGaN/GaN HEMT structures on sapphire substrates to study the impact
of the quality of SiN on the DC, breakdown, small signal and large
signal performance of the device. A maximum increase in the output power
from 1.3 W/mm to 2.3 W/mm at 4 GHz, 20 V bias was observed with a SiN
passivation film, grown in NH3 rich conditions and which gave
the least etch rate of 25 nm/min in buffered oxide etch (6:1). This
increase in power is mainly due to the increase in DC current. This is
clearly shown by plotting the RF dynamic loadline for an unpassivated
and passivated device

  • [Show abstract] [Hide abstract]
    ABSTRACT: AlGaN/GaN heterostructure transistors show potential in high-frequency high-power applications because of their high breakdown voltages and high electron saturation velocities. The operating drain voltage, limiting the maximum RF output power, should be lower than breakdown voltage of the device. The frequency and breakdown properties of the AlGaN/GaN heterostructure transistors have been studied.
    Compound Semiconductors, 2003. International Symposium on; 09/2003
  • [Show abstract] [Hide abstract]
    ABSTRACT: To improve the passivation process of AlGaN/GaN HEMTs, a unique passivation process has been developed in which an SiN passivation layer is deposited by MBE immediately following epitaxial growth of the HEMT structure. The effectiveness of this in situ passivation process is evaluated by comparing devices fabricated with this process to the conventional PECVD passivation process in which the SiN is deposited after gate metallisation. The improved material quality and the protection offered by the MBE-grown SiN may contribute to the significantly reduced dispersion and improved power performance measured for the wafer fabricated with the in situ passivation process.
    Electronics Letters 02/2007; · 1.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Drain current dispersion effects are investigated in AlGaN-GaN HEMTs by means of pulsed, transient, and small-signal measurements. Gate- and drain-lag effects characterized by time constants in the order of 10<sup>-5</sup>-10<sup>-4</sup> s cause dispersion between dc and pulsed output characteristics when the gate or the drain voltage are pulsed. An activation energy of 0.3 eV is extracted from temperature-dependent gate-lag measurements. We show that two-dimensional numerical device simulations accounting only for polarization charges and donor-like traps at the ungated AlGaN surface can quantitatively reproduce all dispersion effects observed experimentally in the different pulsing modes, provided that the measured activation energy is adopted as the energetic distance of surface traps from the valence-band edge. Within this hypothesis, simulations show that surface traps behave as hole traps during transients, interacting with holes attracted at the AlGaN surface by the negative polarization charge.
    IEEE Transactions on Electron Devices 11/2004; · 2.06 Impact Factor