Wafer-bonded heterojunctions is an enabling technology that joins two dissimilar semiconductors which are otherwise difficult to grow epitaxially. This technology can be used to couple a narrow and a wide-bandgap semiconductor to simultaneously accomplish high speed and high breakdown in a transistor. One such transistor is a BAVET- Bonded CAVET (Current Aperture Vertical Electron Transistor). It consists of an In<SUB>0.53</SUB>Ga<SUB>0.47</SUB>As/In<SUB>0.52</SUB>Al<SUB>0.48</SUB>As heterojunction Field Effect Transistor (FET) wafer bonded to an In<SUB>0.1</SUB>Ga<SUB>0.9</SUB>N/GaN epilayer CAVET. The BAVET source lies in high-mobility InGaAs layer and the drain is buried in wide-bandgap GaN layer. The BAVET gate on InAlAs modulates current through a conductive aperture in the InGaN/GaN layer. These vertical apertures are defined by an isolation implant as earlier demonstrated for CAVETs. To achieve a fully functional BAVET, the structural design should meet some key requirements, namely, a strong wafer bonded interface, good current control through both the lateral FET and the vertical BAVET, and a minimal barrier to electron conduction through apertures. This paper reports our progress in achieving the above requirements for the BAVET. In the first demonstration of the BAVET, with implanted GaN layer, reasonable gate modulation and current saturation characteristics are achieved. This illustrates that wafer bonding process does not adversely affect the InGaAs channel. However, this device showed poor pinch-off of channel for both the FET and the BAVET. The pinch-off in FET is prevented by the re-grown InGaN layer acting as a parasitic conduction path underneath the gated region. By implanting the InGaN layer instead, a significant improvement in FET pinch-off is observed. This successfully removes one of the parasitic leakage paths affecting the BAVET characteristics. In Ga-face CAVET template, a thin InGaN interlayer is introduced to reduce the barrier to electron conduction through InGaAs-GaN wafer-bonded junction. The inclusion of InGaN layer, adds another polarization induced barrier to electron flow at InGaN-GaN interface. This barrier sets up a significant turn-on voltage when the device is biased as a BAVET. We are able to mitigate this barrier by intentionally increasing doping in InGaN/GaN layers. And thus, achieve a reduced turn-on voltage in BAVETs. However, high doping in InGaN layer is unfavorable to current blocking properties of implant; consequently affecting BAVET pinch-off. This vertical leakage path through the implanted InGaN layer is in the process of being remedied by optimizing implant and doping at the InGaN-GaN interface. To summarize, we successfully eliminated some of the leakage paths affecting current modulation in BAVETs and reduced the barrier in the apertures. The BAVET characteristics demonstrated in this work have greatly enhanced our understanding of the technology and its design space, enabling a steady progress in achieving bonded heterojunctions for transistor applications. The path to a fully functional BAVET is now clear.