Luminescence and absorption in InGaN epitaxial layers and the van Roosbroeck-Shockley relation

Wurtzite InxGa1-xN (0.01 less than or similar to x less than or similar to 0.14) films have been grown by metalorganic vapor phase epitaxy on sapphire substrates. Integrated photoluminescence intensity and line shapes have be en studied as functions of temperature and alloy composition x. We compare the "effective" InGaN band gap energy assessed by photothermal deflection s pectroscopy with a "mean" band gap energy calculated from room temperature photoluminescence spectra utilizing the van Roosbroeck-Shockley relation an d assuming a Gaussian energy dependence of the subband gap absorption coeff icient. The Stokes' shift between band gap energy and 300 K photoluminescen ce peak is explained by this model. (C) 2000 American Institute of Physics. [S0021- 8979(00)01415-8].