High optical quality polycrystalline indium phosphide grown on metal substrates by metalorganic chemical vapor deposition

Abstract

III–V semiconductor solar cells have demonstrated the highest power conversion efficiencies to date. However, the cost of III-V solar cells has historically been too high to be practical outside of specialty applications. This stems from the cost of raw materials, need for a lattice-matched substrate for single-crystal growth, and complex epitaxial growth processes. To address these challenges, here, we explore the direct non-epitaxial growth of thin poly-crystalline films of III-Vs on metal substrates by using metalorganic chemical vapor deposition. This method minimizes the amount of raw material used while utilizing a low cost substrate. Specifically, we focus on InP which is known to have a low surface recombination velocity of carriers, thereby, making it an ideal candidate for efficient poly-crystalline cells where surface/interface properties at the grain boundaries are critical. The grown InP films are 1-3 μm thick and are composed of micron-sized grains that generally extend from the surface to the Mo substrate. They exhibit similar photoluminescence peak widths and positions as single-crystalline InP, as well as excellent crystallinity as examined through TEM and XRD analyses. This work presents poly-InP as a promising absorber layer for future photovoltaics.