Let say we have a contact of an electron conductor and a hole conductor. How is it possible to prevent recombination of the carriers nearly completely? So, electrons do not suppose to fly or tunnel inside a hole conductor and contra, even if electric potential is applied? Could heterojunctions fit to this purpose?
Imagine having an electric bias (a uniform electric field) across the junction. Electrons appearing will be biased in one direction and the corresponding holes will be biased in the opposite direction. If this can be upheld until they are far enough apart, then recombination will not occur.
This is one of the key working principles of a typical solar cell, where dissimilar materials with dissimilar electron concentrations will get a natural electric field build up in this way due to electron diffusion from one to the other when in contact.