Vapor–liquid–solid growth of highly stoichiometric gallium phosphide nanowires on silicon: restoration of chemical balance, congruent sublimation and maximization of band-edge emission

Growth of high quality III–V compound nanowires using simple chemical vapor deposition method with safe, inexpensive precursors is extremely important for a wide range of applications from solar cells, detectors, to light emitting devices. However, the most-often used deposition approach using compound powers suffers from incongruent sublimation of group III and V elements, leading to premature exhaust of group V elements and eventually to defective, non-stoichiometric nanowires with poor electronic and optical properties. In this paper, we report new results of our efforts in resolving these challenges using as an example the growth of GaP nanowires, an important widegap semiconductor. Our results reveal fascinating roles played by the elemental P source in addition to GaP powder such as restoration of chemical balance, inhabit of the incongruent sublimation of GaP, and the growth of highly stoichiometric GaP NWs with high optical quality and maximized band edge emission. The effects of growth parameters such as growth time, orientations of silicon substrate, growth temperature, and precursor combinations are studied and correlated to stoichiometry of NWs, and to the existence and degree of deep defect states and band edge emission. Our study sheds new light onto the important interplays among all these important factors. Our strategy is not only important for the growth of GaP nanowires on silicon but also for other III–V compounds as well using CVD and inexpensive compound powder sources