Optical properties of GaN epilayers and GaN/AlGaN quantum wells grown by molecular beam epitaxy on GaN(0001) single crystal substrate.
Résumé
GaN epilayers and GaN/AlGaN quantum wells(QWs) were grown by molecular beam epitaxy on GaN(0001) single crystal substrates. Transmission electron microscopy(TEM) was used to assess the crystal quality of the homoepitaxial layers. A dislocation density of less than 105 cm−2 is deduced from TEM imaging. Low temperature (1.8 K) photoluminescence(PL) of homoepitaxial GaN reveals PLlinewidths as low as 0.3 meV for bound excitons. The PL integrated intensity variation between 10 and 300 K is compared to that observed on a typical heteroepitaxialGaN/Al2O3 layer. A 2 nm thick GaN/Al0.1Ga0.9NQW has been studied by time-resolved and continuous wave PL. The decay time is close to a purely radiative decay, as expected for a low defect density. Finally, the built-in polarization field measured in a homoepitaxialQW is shown to be comparable to that measured on heteroepitaxialQWsgrown either on sapphire or silicon substrates.