MOVPE Growth and EQE Artifact Analysis of Upright Metamorphic Quadruple Junction Solar Cell

Abstract

The performance of metal-organic vapor phase epitaxy (MOVPE) grown upright metamorphic (UMM) AlGaInP/AlGaInAs/GaInAs/Ge quadruple junction (QJ) solar cells have been investigated. Metamorphic (MM) epitaxy is achieved through compositionally graded buffer (CGB) layer varying in lattice constants between Ge and Ga0.8In0.2As. High-resolution X-ray diffraction (HRXRD) was used to study the relaxation of strain which is about 98%. Threading dislocation density (TDD) at about 3 × 105 cm−2 was estimated from cathodoluminescence (CL) images. Incorporation of oxygen is effectively suppressed by elevated growth temperature and phosphine flow, which can decrease the nonradiative recombination rate in active layers. Systematic spectra response measurements were used to analyze the comprehensive effect of reverse breakdown (RBD) and luminescence coupling (LC) in multijunction solar cells, including bias light- and voltage-modulated analysis and corresponding analytical models.