부산대학교 도서관

AlN/GaN heterostructures with 1700-$\hbox{cm}^{2}/\hbox{V}\cdot\hbox{s}$ Hall mobility have been grown by molecular beam epitaxy on freestanding GaN substrates. Submicrometer gate-length $(L_{G})$ metal–oxide–semiconductor (MOS) high-electron-mobility transistors (HEMTs) fabricated from this material show excellent dc and RF performance. $L_{G} = \hbox{100}\ \hbox{nm}$ devices exhibited a drain current density of 1.5 A/mm, current gain cutoff frequency $f_{T}$ of 165 GHz, a maximum frequency of oscillation $f_{\max}$ of 171 GHz, and intrinsic average electron velocity $v_{e}$ of $\hbox{1.5} \times \hbox{10}^{7}\ \hbox{cm/s}$. The 40-GHz load-pull measurements of $L_{G} = \hbox{140}\ \hbox{nm}$ devices showed 1-W/mm output power, with a 4.6-dB gain and 17% power-added efficiency. GaN substrates provide a way of achieving high mobility, high $v_{e}$, and high RF performance in AlN/GaN transistors.