Development of wet etch processing for InxAl1−xAsySb1−y solar cells grown on InP

Novel III-V multijunction solar cell concentrator devices grown on InP are potential candidates for achieving efficiencies under AM1.5D illumination of over 50%. Controlled fabrication of these structures involves a complete understanding of the interaction of different wet etch chemistries with the numerous combinations of alloys and semiconductor compounds in this material system. Selective etches for contact layer removal and non-selective etches for mesa isolation were studied for potential processing of an InAlAsSb device lattice-matched to InP. In addition to determining global etch rates for several materials grown on InP, two wet etch chemistries were analyzed in order to optimize a highly selective etch for effective lattice-matched InGaAs contact layer removal. We show that a citric acid-based solution etching of the InGaAs layer resulted in a lateral undercut that was five times greater than etching with a methylsuccinic acid-based solution.