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Indium segregation in Al1-xInxN investigated by photoluminescence under hydrostatic pressure
|Agata Kamińska 1, Grzegorz Staszczak 2, Izabela Gorczyca 2, Andrzej Suchocki 1, Tadeusz Suski 2, David P. Schenk 3|
1. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
The progress in the growth of Al1-xInxN layers has enabled detailed investigation of this material, which is of considerable interest because its band gap Eg covers a very wide spectral range, from the infrared (InN with Eg = 0.7 eV) to the ultraviolet (AlN with Eg = 6.2 eV).
Introducing In to GaN or to AlN improves efficiency of light emission from these materials. Segregation of In seems to play a crucial role in this improvement. Photoluminescence and absorption measurements of Al1-xInxN revealed surprisingly large bowing in the Eg vs. x . Recently I. Gorczyca et al. have performed theoretical calculations of the electronic band structure of Al1-xInxN alloys and their pressure dependence . The calculated band gaps and their pressure coefficients dEg/dp show a decrease for increasing x with especially pronounced bowing of dEg/dp. Moreover, taking into account effect of In segregation causes a decrease in Eg, reduction of dEg/dp and an increase of bowing with respect to In distributed uniformly. Predicted pressure coefficients of Eg for Al1-xInxN with x = 0.25 change drastically from 35 meV/GPa to 15 meV/GPa for uniform and entirely segregated cases, respectively.
In this work we compare these predictions with our experimental results. We analyze the pressure behaviour of light emission for series of Al1-xInxN layers. The measured values of PL peak pressure coefficient are shown to decrease with increasing indium content in accordance with theoretical predictions and are situated between theoretical values calculated for uniform and entirely In-segregated cases. This likely reflects the role of different growth conditions in modifying a rate of In-segregation in Al1-xInxN layers. These results can be useful in understanding and controlling the influence of growth conditions on basic properties of these materials.
 K. Wang et al., J. Appl. Phys. 103, 073510 (2008);
 I. Gorczyca et al., Phys. Stat. Sol. (c) (2009), DOI 10.1002/pssc.200880890.
Presentation: Oral at E-MRS Fall Meeting 2009, Symposium C, by Agata Kamińska
See On-line Journal of E-MRS Fall Meeting 2009
Submitted: 2009-05-08 14:41 Revised: 2009-06-16 10:17