• Grahn, H. T.
• Fernández-Garrido, S.
• Brandt, O.
• Lähnemann, Jonas
• Geelhaar, L.
• Zettler, J. K.
• Hauswald, C.
• Corfdir, P.
• Flissikowski, T.

Abstract

We investigate the nature of excitons bound to I<SUB>1</SUB> basal-plane stacking faults [(I<SUB>1</SUB>,X ) ] in GaN nanowire ensembles by continuous-wave and time-resolved photoluminescence spectroscopy. Based on the linear increase of the radiative lifetime of these excitons with temperature, they are demonstrated to exhibit a two-dimensional density of states, i.e., a basal-plane stacking fault acts as a quantum well. From the slope of the linear increase, we determine the oscillator strength of the (I<SUB>1</SUB>,X ) and show that the value obtained reflects the presence of large internal electrostatic fields across the stacking fault. While the recombination of donor-bound and free excitons in the GaN nanowire ensemble is dominated by nonradiative phenonema already at 10 K, we observe that the (I<SUB>1</SUB>,X ) recombines purely radiatively up to 60 K. This finding provides important insight into the nonradiative recombination processes in GaN nanowires. First, the radiative lifetime of about 6 ns measured at 60 K sets an upper limit for the surface recombination velocity of 210 cm<SUP>s -1</SUP> considering the nanowires mean diameter of 50 nm. Second, the density of nonradiative centers responsible for the fast decay of donor-bound and free excitons cannot be higher than 6 ×10<SUP>16</SUP> cm<SUP>-3</SUP>. As a consequence, the nonradiative decay of donor-bound excitons in these GaN nanowire ensembles has to occur indirectly via the free exciton state....

Topics

• density
• impedance spectroscopy
• surface
• photoluminescence
• strength
• two-dimensional
• stacking fault