Growth and characterization of GaAs nanowires for photovoltaic applications.

Abstract

In this project MBE growth and microfabrication processes are employed to study the growth and characterisation of nanowires for photovoltaic applications, and to fabricate the nanowire solar cell.

III-V semiconductor nanowires are one promising candidate for third generation solar cells. The key advantage of such nanostructure is low cost due to less material used for fabrication. One interesting feature of III-V nanowire is lattice mismatched materials can be integrated in the form of nanowires. The nanowire solar cell can be realized by growing pn junction in two configurations – axial and radial structures. In this project one branch is being studied which is radial nanostructures grown on GaAs(111)B substrates.

GaAs nanowires were grown on both Silicon and GaAs substrates. The difference in physical properties and growth conditions were discussed. Gallium arsenide p-i-n radial nanostructures were fabricated by using molecular beam epitaxy. Physical properties of MBE-grown nanowires were discussed by viewing them under Scanning Electron Microscope(SEM). The growth procedure and microfabrication steps were followed succesfully. The current-voltage characteristics of single core-shell nanowires were measured both in the dark and under illumination. The highest efficiency was 2.4%. The fill factor for this best result was 43%. According to these achieved results, nanowires promise better progress for the use in photovoltaic applications.