Abstract
Temperature-dependent photoluminescence (PL) spectroscopy is carried out to probe radiative recombination and related light emission processes in two-dimensional periodic close-packed nanopore arrays in gallium nitride (np-GaN). The arrays were produced by nonlithographic nanopatterning of wurtzite GaN followed by a dry etching. The results of Raman spectroscopy point to a small relaxation of the compressive stress of ~0.24 GPa in nanoporous vs. bulk GaN. At ~300 K, the PL emission is induced by excitons and not free-carrier interband radiative recombinations. An evolution of the emission spectra with T is confirmed to be mainly a result of a decay of nonexcitonic PL emission and less of spectral shifts of the underlying PL bands. A switching of excitonic PL regime observed experimentally was analyzed within the exciton recombination-generation framework. The study provides new insights into the behaviors and physical mechanisms regulating light emission processes in np-GaN, critical to the development of nano-opto-electronic devices based on mesoscopic GaN.
Highlights
For its advanced electronic, optical, and physical characteristics including a direct band gap, excellent thermal conductivity, and electron mobility > 1400 cm2/Vs, GaN remains one of the key, technologically advanced wide-band-gap semiconductors. [1,2,3]
While bulk GaN devices continue to be a focus of experimental and theoretical research, a significant effort has been recently devoted to producing crystalline nanoporous GaN films and templates [7,8,9]
As we reported previously, highly ordered, high-density nanoporous GaN (np-GaN) can be readily produced by reactive ion etching (RIE) of GaN epilayers while using nanoporous regimented free-standing alumina as a top etching mask [9]
Summary
Optical, and physical characteristics including a direct band gap, excellent thermal conductivity, and electron mobility > 1400 cm2/Vs, GaN remains one of the key, technologically advanced wide-band-gap semiconductors. [1,2,3]. While bulk GaN devices continue to be a focus of experimental and theoretical research, a significant effort has been recently devoted to producing crystalline nanoporous GaN (np-GaN) films and templates [7,8,9]. These mesostructures feature a number of profoundly different characteristics that can help propel applications of GaN beyond electronics. Future device uses, in this study, we investigate the structural, strain and light emission characteristics of np-GaN produced by SOSA by performing a large-area scanning electron microscope imaging, Raman, optical reflection, temperature, and intensity-dependent photoluminescence spectroscopic characterizations, the details of which are presented and discussed below
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