  In this paper, we have characterized an AlGaN/GaN High Electron Mobility
Transistor (HEMT) with a short gate length (Lg $\approx$ 0.15$\mu$m). We have
studied the effect of short gate length on the small signal parameters,
linearity parameters and gm-gd ratio in GaN HEMT devices. To understand how
scaling results in the variation of the above-mentioned parameters a
comparative study with higher gate length devices on similar heterostructure is
also presented here. We have scaled down the gate length but the barrier
thickness(t$_{bar}$) remained same which affects the aspect ratio
(L$_{g}$/t$_{bar}$) of the device and its inseparable consequences are the
prominent short channel effects (SCEs) barring the optimum output performance
of the device. These interesting phenomena were studied in detail and explored
over a temperature range of -40$^\circ$C to 80$^\circ$C. To the best of our
knowledge this paper explores temperature dependence of SCEs of GaN HEMT for
the first time. With an approach to reduce the impact of SCEs a simulation
study in Silvaco TCAD was carried out and it is observed that a recessed gate
structure on conventional heterostructure successfully reduces SCEs and
improves RF performance of the device. This work gives an overall view of gate
length scaling on conventional AlGaN/GaN HEMTs.
