Selective-area growth of single-crystal wurtzite GaN nanorods on SiOx/Si(001) substrates by reactive magnetron sputter epitaxy exhibiting single-mode lasing

Yu-Lin Tsai,Hao-Chung Kuo,Justinas Palisaitis,Jens Birch,Lars Hultman,Elena Alexandra Serban,Muhammad Junaid,Hsu-Cheng Hsu,Chia-Cheng Yeh,Per Ola Åke Persson,Ching-Lien Hsiao

doi:10.1038/s41598-017-12702-y

Abstract

Selective-area growth (SAG) of single-crystal wurtzite GaN nanorods (NRs) directly onto Si(001) substrates with un-etched native SiOx amorphous layer, assisted by a patterning TiNx mask fabricated by nanosphere lithography (NSL), has been realized by reactive magnetron sputter epitaxy (MSE). The GaN NRs were grown vertically to the substrate surface with the growth direction along c-axis in the well-defined nano-opening areas. A 5-step structural and morphological evolution of the SAG NRs observed at different sputtering times depicts a comprehensive growth model, listed in sequence as: formation of a polycrystalline wetting layer, predominating c-axis oriented nucleation, coarsening and coalescence of multi-islands, single NR evolution, and finally quasi-equilibrium crystal shape formation. Room-temperature cathodoluminescence spectroscopy shows a strong GaN bandedge emission with a uniform luminescence across the NRs, indicating that the SAG NRs are grown with high quality and purity. In addition, single-longitudinal-mode lasing, attributed to well-faceted NR geometry forming a Fabry–Pérot cavity, was achieved by optical pumping, paving a way for fabricating high-performance laser optoelectronics using MSE.

Highlights

The selective-area growth (SAG) of nanorods (NRs), by the use of patterned substrates, presents the advantages of resultant NRs with uniform size leading to uniform properties, and site-specific controlled growth[1,2,3,4,5]
The NR geometry allows for an increased photon extraction efficiency[1], and the use of Selective-area growth (SAG) NRs has been successfully demonstrated in the fabrication of single color and monolithic integration of red-green-blue (RGB) high-brightness light-emitting diodes (LEDs)[2,3,4]
Plenty of research studies exist on SAG of GaN NRs by metal-organic chemical vapor deposition (MOCVD)[3,16,17] and molecular-beam epitaxy (MBE)[2,4,18,19], no work has been performed by magnetron sputter epitaxy (MSE)

Summary

Introduction

The selective-area growth (SAG) of nanorods (NRs), by the use of patterned substrates, presents the advantages of resultant NRs with uniform size leading to uniform properties, and site-specific controlled growth[1,2,3,4,5]. The NR geometry allows for an increased photon extraction efficiency[1], and the use of SAG NRs has been successfully demonstrated in the fabrication of single color and monolithic integration of red-green-blue (RGB) high-brightness light-emitting diodes (LEDs)[2,3,4]. An ordered array characterized by uniformity in sizes and shapes is desired in high-density integration and chip processing technology. Among others, this could be implemented in the replacement of conventional planar LEDs in the solid-state lighting market. In the other cases of MBE and MOCVD processes, temperatures higher than 700 °C are often required to obtain high-quality films since the mobility of adatoms is mainly contributed from thermal energy[22,23]

Methods

Results

Conclusion