Wafer-bonded current aperture vertical electron transistors (BAVETs) aim to eliminate the present bottleneck of simultaneously achieving high frequency and high breakdown. BAVETs enable novel transistors with a high mobility III-As (mobility = 12000 cm2 V−1S−1) channel, and a wide-bandgap III-N (breakdown field = 3.3MV.cm-1) drift region. A BAVET device, based on a current aperture vertical electron transistor (CA VET), comprises source contacts to n-doped $\mathrm{In}_{0.53}\mathrm{Ga}_{0.47}\mathrm{As}$ channel, with $\mathrm{I}\mathfrak{n}_{0.52}\mathrm{Al}_{0.48}\mathrm{As}$ as the gate barrier, InGaN/GaN layers for the drift region, and n+GaN as the drain-contact layer (Fig. 1) [1]. The on-state DC performance in a BAVET has been traditionally affected by abnormally high on-current-saturation voltage, $V_{\mathrm{DS}_{-}\mathrm{SAT}}(> 12\mathrm{V})$ (Fig. 2) [2]–[4]. Herein, we investigate the cause of this abnormality and report a significant reduction in $\mathrm{V}_{\mathrm{DS}_{-}\mathrm{SAT}}(5\mathrm{V})$.