Of course - in any device in ATK, the central region can be anything - incl. defects, extra layers, and so on. But I'm also not sure I understand the exact question, because this cartoon is exactly a "normal" device for me, so why wouldn't there be transport? That is, I don't understand why it's not a normal device. Of course if the vacuum gap (?) is very wide, transport is suppressed but as long as there is a basis set overlap between atoms in materials A and B, the electrons can tunnel across the gap.