Growth of InGaAs solar cells on InP(001) miscut substrates using solid-source molecular beam epitaxy

Abstract

In this work, we studied effects of both the growth temperature and the substrate miscut on the properties of lattice-matched InGaAs solar cells, which were grown on InP(001) by solid-source molecular beam epitaxy. In atomic force microscopy, root-mean-square roughness was 0.14 nm for the cell grown on InP(001) miscut 2° toward (111)A (2°A) at 490°C, which was smaller than that of 0.18 nm for the cell grown on the exactly-cut substrate (exact) at 420°C. In addition, we observed clear step structures along [1-10] direction for the 2°A cell, suggesting the promoted step-flow growth. In photoluminescence (PL) measurements, PL emissions at 1640 nm with linewidth of 63 meV were clearly observed for all cells, while the PL emission for the 2°A cell grown at 490°C was the largest among them. Consequently, the 2°A cell yielded the highest efficiency of 12.3% compared with that of 9.7% for the exact cell grown at 420°C. These results suggest that promotion of the step-flow growth mode enhances the quality of InGaAs films leading to improving the cell performance.