Probing the Electronic States in GaAsNBi Alloys*

Although solar energy is the most abundant renewable energy source, an approach to combine energy harvesting and energy storage is urgently needed. Recently, solar to hydrogen (STH) conversion using photoelectrochemical cells (PEC) has emerged as a promising approach to harvest and store solar energy. Indeed, record STH efficiency is predicted for a tandem PEC which includes a 1.05 eV bandgap junction.¹ Recently, we synthesized a novel alloy, gallium arsenide nitride bismide,² which is nearly lattice-matched to gallium arsenide, with bandgaps tunable from 0.87 to 1.34 eV. To determine the energy bandoffsets and electronic states of GaAsNBi alloys, we are examining GaAs/GaAsNBi/GaAs single quantum well structures with dilute concentrations of N and Bi. Using a combination of photoluminescence spectroscopy, in conjunction with capacitance-voltage measurements and 1D-Schrödinger-Poisson simulations, we determine the band offsets and deep levels in GaAs/GaAs_1-x-yN_xBi_y/GaAs heterostructures.
¹J. L. Young, M.A. Steiner, H. Doscher, R.M. France, J.A. Turner, T.G. Deutsch, Nature Energy, 17028 (2017).
²J. Occena, T. Jen, E.E. Rizzi, T.M. Johnson, J. Horwath, Y.Q. Wang, R.S. Goldman, Appl. Phys. Lett.110, 242102 (2017).