Epitaxial growth of InGaAs on MgAl2O4 spinel for one-sun photovoltaics

Abstract We demonstrate coincident-site lattice-matched growth of InGaAs layers on (001) MgAl 2 O 4 spinel substrates, using a 45° rotation between the lattices, by molecular beam epitaxy. This is the first step towards easily removable multijunction solar cells with inert, reusable substrates. High-resolution cross-sectional transmission electron microscopy (TEM) measurements indicate that microtwins originate at the InGaAs/spinel interface, but tend to annihilate leaving the upper parts of layers relatively twin-free. Plan-view TEM indicates a high density of threading dislocations. InGaAs layers grown at elevated temperatures show improved transport properties, with majority-carrier mobilities approaching typical values for homoepitaxial GaAs on GaAs substrates. Simple p – i – n junctions show photovoltaic efficiencies above 1%.