Photoluminescence of InGaN/GaN quantum wells grown on c-plane substrates with locally variable miscut

Growth of high-quality nitride-based structures requires use of miscut substrates, which means that the growth plane is tilted with respect to the c lattice plane (0001). In order to investigate the miscut influence on grown layers, patterned GaN substrates with separate regions tilted between 0.34 degrees and 0.97 degrees to the c-plane were used to grow multiquantum well InGaN/GaN structures by metalorganic vapor phase epitaxy. The quantum wells had a nominal 6% indium content. Precise values of miscut in each region were determined by atomic-force microscopy. Recombination dynamics in each region was studied using time-resolved microphotoluminescence (PL) from 4K to room temperature. It was found that the PL energy increases with miscut angle from 3.17 to 3.29eV (at 4K). The PL lifetime also correlated with the miscut angle, it decreased from 1.2 down to 0.8ns (at 4K). These results suggest that an increase of the angle causes a decrease of the indium content. Less indium naturally leads to a higher bandgap, and to reduction of electric field inside the quantum wells (QWs). Both effects lead to a PL energy increase. Moreover, the decrease of the electric field reduces the electron-hole separation that explains the shorter radiative recombination at 4K at regions of high-miscut angles. The shape of temperature dependence of PL decay times suggests that at low temperatures PL decay is determined by the localization of carriers, whereas in room temperature LO phonon-assisted delocalization processes play a dominant role.