The high band-bending in the surface of n-GaN creates a "notch" for holes generated in a PL experiment that does not exist in the "bulk" underneath. This opens new ways to emit photons other than the band to band recombination that takes place in the bulk for example. Do we really need to "dope" the GaN bulk with trapping centres to explain a yellow emission in PL that can come from the GaN surface?
Article Surface-Assisted Luminescence: the PL Yellow Band and the EL...
Briefly, photoluminescence was never bulk effect. Excitation of photoluminescence for semiconductor materials demand to use photon energy larger than the band gap. In this case strong absorption occurs. Therefore, photoluminescence due to the near-surface layer with thickness of less than 1 micron. Certainly, there are the surface states which act as traps for electrons or holes. Therefore, the influence of the surface on the photoluminescence of semiconductor materials can be substantial. But even more significant is to establish the nature of the surface centers and the ability to manage their concentration. Also important is their stability, since that determines the use of these materials in the development of various devices.
Dear Yu Gnatenko:
Viewing your first sentence, welcome to the "heresy club". I´ll repeat it here "Briefly, photoluminescence was never bulk effect.". Have you read my paper in ArXiv? What if some weak PL from GaN (weak luminescence found in PL experiments) was surface EL (ElectroLuminescence) as I propose? We could predict (as I have done) the weak EL that researchers are finding in GaN transistors and the GaN photoconductance (not photoconductivity, nobody measures photoconductivity, this is a widespread MISCONCEPTION) measured years ago..... Three phenomena explained by the same physical mechanism.....Unifying, interesting
When I am under the sunlight behind the glass of my window and I don't become tanned, I don´t say "This sun doesn´t emit UV radiation"., although it would be possible. Instead, I prefer to consider the filtering action of the thin glass of my window, and this would show the difference between theoretical engineering and applied physics considering today's beliefs on the subject.. Given your answer that supports my viewpoint to a high extent, my question remains open.....
I see that you have some problems ... Maybe you need to turn to another forum?
