Advancement in the MOVPE technology to increase the process yield and expand the band gap engineering possibilities

New approaches to MOVPE material deposition have been developed in order to increase the process yield and expand the band gap engineering possibilities for the realization of high efficiency multijunction (MJ) solar cells. Paradigm changes in the MOVPE growth chamber design have been introduced in order to maintain high thermal homogeneity at the wafer surface also in the case of the growth of strained structures and to allow getting a fast temperature control at the interfaces between arsenide and phosphide materials. Furthermore, the growth chamber design has been modified in order to remove the growth incompatibility among III-V and group IV elements of the period table. A significant step ahead has been accomplished in reducing the cross doping effects coming from the utilization of the different semiconductor materials, thus opening the path towards the realization of “all MOVPE grown” III-V/IV based MJ solar cells (like for example the InGaP/InGaAs/SiGeSn/Ge quadruple junction solar cells). As a proof of the concept, SiGe layers with high structural quality have been grown in the same MOVPE reactor used to growth InGaP/InGaAs/Ge MJ solar cell structures and a first demonstration of a properly working InGaP/InGaAs/SiGe/Ge TJ solar cell is presented.