Editing Photoluminescence (section)

=== Effects of disorder ===
Real material systems always incorporate disorder. Examples are structural  [[Crystallographic defect|defects]]<ref>{{cite journal|doi=10.1088/0022-3727/47/42/423001|arxiv=1405.1261|bibcode=2014JPhD...47P3001L|title= Luminescence associated with stacking faults in GaN|journal=J. Phys. D: Appl. Phys. | volume = 47 | issue = 42 | pages = 423001 | year = 2014 | last1 = Lähnemann | first1 = J. | last2 = Jahn | first2 = U. | last3 = Brandt | first3 = O. | last4 = Flissikowski |first4=T.|last5=Dogan|first5=P.|last6=Grahn|first6=H.T.|s2cid=118671207}}</ref>  in the lattice or [[Order and disorder (physics)|disorder]] due to variations of the chemical composition. Their treatment is extremely challenging for microscopic theories due to the lack of detailed knowledge about  perturbations of the  ideal structure. Thus, the influence of the extrinsic effects on the PL is usually addressed phenomenologically.<ref name="BaranovskiiEichmann1998">Baranovskii, S.; Eichmann, R.; Thomas, P. (1998). "Temperature-dependent exciton luminescence in quantum wells by computer simulation". ''Physical Review B'' '''58''' (19): 13081–13087. [https://dx.doi.org/10.1103%2FPhysRevB.58.13081 doi:10.1103/PhysRevB.58.13081.]</ref> In experiments, disorder can lead to localization of carriers and hence drastically increase the photoluminescence life times as localized carriers cannot as easily find nonradiative recombination centers as can free ones.

Researchers from the [[King Abdullah University of Science and Technology (KAUST)]] have studied the photoinduced [[entropy]] (i.e. thermodynamic disorder) of [[InGaN]]/[[GaN]] p-i-n [[double-heterostructure]] and [[AlGaN]] [[nanowires]] using temperature-dependent photoluminescence.<ref name="entropyalfaraj2017"/><ref name="entropyalfaraj2017_1">Alfaraj, N.; Mumthaz Muhammed, M.; Li, K.; Janjua, B.; Aljefri, R. A.; Sun, H.; Ng, T. K.; Ooi, B. S.; Roqan, I. S.; Li, X. (2017). "Thermodynamic photoinduced disorder in AlGaN nanowires". ''AIP Advances'' '''7''' (12): 125113. [https://doi.org/10.1063/1.5003443]</ref> They defined the photoinduced [[entropy]] as a thermodynamic quantity that represents the unavailability of a system's energy for conversion into useful work due to [[carrier recombination]] and [[photon]] emission. They have also related the change in entropy generation to the change in photocarrier dynamics in the nanowire active regions using results from time-resolved photoluminescence study. They hypothesized that the amount of generated disorder in the [[InGaN]] layers eventually increases as the temperature approaches room temperature because of the thermal activation of [[surface states]], while an insignificant increase was observed in AlGaN nanowires, indicating lower degrees of disorder-induced uncertainty in the wider bandgap semiconductor. To study the photoinduced [[entropy]], the scientists have developed a mathematical model that considers the net energy exchange resulting from photoexcitation and photoluminescence.