According to Wang et. al. (Chem. Soc. Rev., 2014, 43, 5234--5244), the S–S heterojunction systems can be divided into two different types: p–n semiconductor heterojunction and non-p–n heterojunction systems. However, I cannot tell their difference briefly. Does anyone have comment?
There are two types of heterojunctions: conventionel p-n type, called "anisotype" and n-n or p-p type heterojunctions , called "isotype" (non conventionnel), based on two semiconductors with the same semi-conductivity character and differents Fermi levels, Eg, ... There is much bibliography on this type of heterojunctions; a lot of them concern organic semiconducteurs.
In that review, a p-n junction includes a depletion region and built-in field from charge transfer during equilibration. For sufficiently thick junctions this always occurs to some degree except for the case where the electron affinities and doping levels result in the Fermi levels in the two materials being at very similar absolute energies before being brought into contact (fairly unlikely). Therefore a non p-n junction appears to be for the case for nano-scale junctions, where photocarrier collection occurs via the band offsets. For any heterojunction of sufficient thickness you will need to consider the band alignment of the different materials and p-n equilibration effects. I'm not sure if I agree that this distinction is that useful, especially since it is not mentioned again in the article. I wouldn't get too confused by unconventional naming and organizational schemes. For a better understanding of heterojunctions I would go through some of the early work on this subject, by Anderson (doi:10.1016/0038-1101(62)90115-6), Tersoff (doi:10.1103/PhysRevB.30.4874) and Kroemer (doi:10.1080/10408437508243512, 10.1016/0039-6028(83)90561-7, 10.1016/0039-6028(86)90425-5).
Thanks to all of your suggestion, the lake is more limpid now.
According to my understanding after further researching, I also agree with non-p-n heterojunction is a structure formed by contact of n-n or p-p materials with different band position ans bad gap. It's not a new concept but a description.
To Mr. May: I even read that effect between opposed interaction between nanoparticle size and space-charge region. It seems that to efficiently separate charge carriers, the size should be take into account seriously.
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