Quantum-confined stark effect in localized luminescent centers within InGaN/GaN quantum-well based light emitting diodes

The nature of the polarization-field in disorder induced nanoscale potential fluctuations (radiative traps) within (In,Ga)N based quantum-well (QW) heterostructures remains ambiguous. Spectrally resolved photoluminescence microscopy has been utilized to probe the local polarization field by monitoring the extent of quantum-confined Stark effect (QCSE) in radiative trap centers spontaneously formed within an (In,Ga)N QW based light emitting diode. Interestingly, two distinct categories of nanoscale radiative domains, which arise from indium compositional and interface-morphology related fluctuations of the active layers, are found to have very different degree of built-in polarization fields. Screening of QCSE in indium-rich emission centers results in blue-shift of transition energies by up to 400 meV, significantly higher than that reported previously for group III-nitride based semiconductor heterostructures. A lack of correlation between the extent of QCSE and local indium mole-fractions suggests that size, shape, and strain of individual localization centers play a crucial role in modulating the local polarization field.