Localization Effects in InGaN/GaN Double Heterostructure Laser Diode Structures Grown on Bulk GaN Crystals.
Résumé
We demonstrate a double heterostructure (DH) nitride laser diode (LD) with an untypically wide 9.5 nm InGaN active region instead of the commonly used narrow InGaN quantum wells. Structures were grown on bulk GaN, which ensures low dislocation densities and therefore low concentrations of nonradiative recombination centers. The efficient screening of polarization induced electric fields in the structures under investigation, which contained heavily (1×1019 cm-3) Si doped barriers, was demonstrated by means of hydrostatic pressure dependent photoluminescence measurements on a simplified sample with identical active region. Since the detrimental separation of carriers by electric fields becomes more pronounced for wider InGaN active regions, efficient screening of polarization induced electric fields is essential for the investigated heterostructures. Optical and electrical parameters of this LD were comparable to those of comparable devices with typical QWs of ~4 nm as active region. We observed a high thermal stability of the photoluminescence intensity and, via time-resolved photoluminescence, a relatively temperature-independent radiative decay time. These observations support the significance of carrier localization phenomena for the radiative recombination processes of the investigated structure. The implications of these results for DH LD structures are discussed.