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

The effects of power and time conditions of in situ 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 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 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 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.