Patterning optimization for device realization of patterned GaAsSbN nanowire photodetectors.

Abstract

Vertically grown nanowires are a research interest in optoelectronics and photovoltaic applications due to their high surface to volume ratio and good light trapping capabilities. This study presents the effects of process and design parameters on self-catalyzed GaAsSbN nanowires (NWs) grown by plasma-assisted molecular beam epitaxy on patterned silicon substrates using electron beam lithography. Vertical alignment of the patterned NWs examined via scanning electron microscopy show the sensitivity of patterned nanowire growth to the parameters of nanowire diameter, pitch, dose time, etching techniques and growth plan. Diameters range from 90 nm to 250 nm. Pitch lengths of 200 nm, 400 nm, 600 nm, 800 nm, 1000 nm, and 1200 nm were examined. Dry etching of the oxide layer of the silicon substrate and PMMA coating is performed using reactive ion etching for 20 s and 120 s respectively. Comparisons of different HF etch durations performed pre and post PMMA removal are presented. Additionally, the report of an observed surfactant effect in dilute nitride GaAsSbN nanowires in comparison to non-nitride GaAsSb is presented. Optimizations to patterning, reactive ion etching, and HF etching are presented to obtain higher vertical yield of patterned GaAsSbN nanowires, achieving ~80% of the expected NW/µm2. Room temperature and 4K photoluminescence results show the effect of nitride incorporation for further bandgap tuning, and patterned pitch on the optical characteristics of the nanowires which gives insights to the compositional homogeneity for nanowires grown at each pitch length.