The progress in the growth of Al_1-xIn_xN layers has enabled detailed investigation of this material, which is of considerable interest because its band gap E_g covers a very wide spectral range, from the infrared (InN with E_g = 0.7 eV) to the ultraviolet (AlN with E_g = 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 Al_1-xIn_xN revealed surprisingly large bowing in the E_g vs. x [1]. Recently I. Gorczyca et al. have performed theoretical calculations of the electronic band structure of Al_1-xIn_xN alloys and their pressure dependence [2]. The calculated band gaps and their pressure coefficients dE_g/dp show a decrease for increasing x with especially pronounced bowing of dE_g/dp. Moreover, taking into account effect of In segregation causes a decrease in E_g, reduction of dE_g/dp and an increase of bowing with respect to In distributed uniformly. Predicted pressure coefficients of E_g for Al_1-xIn_xN 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 Al_1-xIn_xN 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 Al_1-xIn_xN layers. These results can be useful in understanding and controlling the influence of growth conditions on basic properties of these materials.

References:

[1] K. Wang et al., J. Appl. Phys. 103, 073510 (2008);

[2] I. Gorczyca et al., Phys. Stat. Sol. (c) (2009), DOI 10.1002/pssc.200880890.

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