Excitons AlGaN

B OPTICAL BANDGAP AND LUMINESCENCE PROPERTIES OF AlGaN IN THE EXCITONIC REGION... 

TABLE 1 Summary of the bowing parameter of optical bandgap and excitonic bandgap of AlGaN reported to date. 

It has been proposed recently that phase separation of GalnN into In-rich and Ga-rich phases has profound consequences on the optical properties and on the lasing properties of GalnN/GaN/AlGaN quantum well heterostructures [1,2]. The nanoscale compositional fluctuations resulting from phase separation are believed to lead not only to exciton localisation [2] but even to a quantum-dot-like behaviour [3], A more detailed discussion of the microscopic aspects of phase separation is given elsewhere in this volume. 

Similar results were obtained from n-Mgo.iZn<) 90/n-ZnO/p-Alo.i6Gao.84N/p-GaN triple heterostructure LEDs fabricated by Osinsky et al. [100]. The strong electroluminescence at 390 nm, observed under forward bias, was attributed to excitonic recombination in the ZnO layer. These results show that p-AlGaN is a good candidate for fabricating efficient heterostructure LEDs with ZnO active layers. 

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