Impact of Gate-Aperture Overlap on the Channel-Pinch Off in InGaAs/InGaN-Based Bonded Aperture Vertical Electron Transistor

A unipolar transistor consisting of an In_0.53Ga_0.47As (InGaAs) channel and a III-Nitride (III-N)-based drain-region with a maximum on-current of 192 mA/mm is reported. This unique device is realized by employing wafer-bonding to a current aperture vertical electron transistor and is referred to as a wafer-bonded aperture vertical electron transistor (BAVET). An In_0.52Al_0.48As/InGaAs layer-stack is used for the gate-barrier and channel regions, while the aperture, current-blocking-layer (CBL) and drift regions are part of the III-N layer structure. This letter investigates the factors affecting the off-characteristics of a BAVET by varying the overlaps of the gate-CBL (L_GO) and gate-aperture (L_GA) regions. A dual-functionality of modulating the channel and providing a field-plate effect is realized using the L_GO and L_GA parts of the gate, respectively. We report that the improvement in channel-pinch off is a stronger function of L_GA than it is of L_GO. A weak pinch off in the InGaAs channel is shown to be the consequence of impact-ionization leading to channel-breakdown, and using a gate-aperture overlap dramatically improves both the pinch off and off-state-breakdown in BAVETs.