The effect of Si-doping on the variable temperature photoluminescence properties of AlGaN alloys

Abstract

A study of the optical properties of a series of undoped and Si-doped AlxGa1-xN layers has been performed using variable temperature photoluminescence (PL) measurements. The Al mole content, x, of the AlxGa1-xN layers, grown by metalorganic vapour phase epitaxy (MOVPE) on c-sapphire substrates, was varied between 0 and 0.5. The PL properties of the layers were studied between 12 and 300 K. The PL peak energy exhibited the anomalous "S-curve" behaviour (increase-decrease- increase) with increasing temperature. This anomolous behaviour was seen to be more pronounced in the Si-doped material, and subsequently a larger localization energy was measured for these samples. The thermal quenching of the integrated PL intensity was well fitted assuming that two non-radiative channels are present in the layers, thus yielding two PL activation energies. These activation energies are then compared to the Hall effect activation energy. From a correlation between the low temperature PL activation energy and the Hall activation energy, the low temperature quenching of the integrated PL intensity is attributed to the delocalisation of excitons bound to neutral Si donors. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.