Optical Properties and Defect Formation in Gallium Phosphide/Gallium Nitrogen Phosphide Core/Shell Nanowires

Monday, 6 October 2014: 16:30
Expo Center, 1st Floor, Universal 6 (Moon Palace Resort)
A. Dobrovolsky, J. E. Stehr (Linkoping University), Y. J. Kuang, S. Sukrittanon, C. W. Tu (University of California, La Jolla), W. M. Chen, and I. A. Buyanova (Linkoping University)
III-V semiconductor nanowires (NWs) have recently attracted increasing attention due to their potential applications in optoelectronic and photonic devices. Among all III-V compounds, GaP-based materials have the smallest lattice mismatch to Si are, therefore, among the best candidates for growth of III-V core/shell NWs on silicon. Adding a small amount of N in GaP allows one to further minimize this mismatch and also leads to transformation of the band gap character from an indirect one in GaP to a direct-like one in the GaNP alloys, leading to improvements in efficiency of light emission.

In this work we evaluate radiative efficiency of novel GaP/GaNP core/shell NWs grown on Si substrates by using comprehensive optical characterization techniques, including cw- and time-resolved photoluminescence (PL) spectroscopies and optically detected magnetic resonance (ODMR). Superior optical quality of the structures is demonstrated from the observation of intense PL emission from a single NW at room temperature (RT). This emission is concluded to originate from radiative transitions within N-related localized states, based on the results from the temperature dependent cw- and time-resolved PL studies. In spite of the high optical quality, the RT carrier lifetime in the structures is still found to be governed by non-radiative recombination processes as evident from the results of the time-resolved PL measurements. ODMR studies identified a defect complex involving a P atom at its core as a non-radiative recombination center in the GaNP shell, most likely located at the GaP/GaNP interface.