Impact of $\hbox{N}_{2}$ Plasma Power Discharge on AlGaN/GaN HEMT Performance

The effects of power and time conditions of in situ
$\hbox{N}_{2}$
plasma treatment, prior to silicon nitride (SiN) passivation, were investigated on an AlGaN/GaN high-electron mobility transistor (HEMT). These studies reveal that
$\hbox{N}_{2}$
plasma power is a critical parameter to control the SiN/AlGaN interface quality, which directly affects the 2-D electron gas density. Significant enhancement in the HEMT characteristics was observed by using a low power
$\hbox{N}_{2}$
plasma pretreatment. In contrast, a marked gradual reduction in the maximum drain–source current density
$(I_{DS \max})$
and maximum transconductance
$(g_{m \max})$
, as well as in
$f_{T}$
and
$f_{\max}$
, was observed as the
$\hbox{N}_{2}$
plasma power increases (up to 40% decrease for 210 W). Different mechanisms were proposed to be dominant as a function of the discharge power range. A good correlation was observed between the device electrical characteristics and the surface assessment by atomic force microscopy and Kelvin force microscopy techniques.