Novel approaches to MOVPE material deposition for high efficiency Multijunction Solar Cells

Abstract

Starting from a brief survey on the most important III‐V material engineering approaches which brought multijunction solar cells reaching an efficiency value of 44.7% to realization, new approaches to MOVPE material deposition are presented to further incrementing the solar cell performances and reduce the technology cost. A new MOVPE temperature profile tuning capability has been developed in order to maintain high thermal homogeneity at the wafer surface, also in the case of the deposition of strained structures, as well as to get a fast temperature control at the interfaces between arsenide and phosphide materials. Preliminary results on the possibility to combine group III‐V with group IV elements in the same MOVPE growth chamber in order to expand the band gap engineering possibilities are also presented and demonstrated at device level. As a proof of the concept, SiGe layers have been grown in the same MOVPE reactor used to grow III‐V compounds and InGaP/InGaAs/Ge Multijunction solar cell structures have been realized and characterized after SiGe deposition.