Suppression of Drain Current Leakage and Short-Channel Effect in Lateral Ga2O3 RF MOSFETs Using (AlxGa1-x)2O3 Back-Barrier

An (AlxGa1-x)2O3 back-barrier was inserted into lateral Ga2O3 RF MOSFETs to suppress both the drain current (
${I}_{\text {d}}$
) leakage through an epilayer/substrate interface and the short-channel effect. The
${I}_{\text {d}}$
leakage was suppressed to a sufficiently low value of less than 1 nA/mm. As for the small-signal RF characteristics, a peak current gain cutoff frequency (
${f}_{\text {T}}$
) of 10 GHz and a peak maximum oscillation frequency (
${f}_{\text {max}}$
) of 24 GHz were obtained with gate length of 120–150 nm. Compared to our previous work without a back-barrier, a peak
${f}_{\text {max}}$
appeared at the shorter gate length by 50–80 nm. Therefore, the insertion of an (AlxGa1-x)2O3 back-barrier was effective to suppress the
${I}_{\text {d}}$
leakage and to a certain extent the short-channel effect. Delay-time analysis using a simplified small-signal equivalent circuit model indicates that increasing the AC transconductance and decreasing the extrinsic delay are the keys to achieve higher
${f}_{\text {T}}$
.