A substrate removal processing method for III-V solar cells compatible with low-temperature characterization

In this work, we present a substrate removal procedure for solar cells compatible with direct attachment of the epitaxy to a holder through a thermally and electrically conductive interface. In our case this procedure was motivated by the need to develop a processing technique compatible with low-temperature characterization of the devices. The method is based on the use of indium to bond a thin-film epitaxial structure to a silicon support. The adequate properties of indium, namely, low tensile strength and good thermal and electrical conductivity, allow characterizing the devices at very low temperatures without causing strain-induced degradation in the samples. Following this method, we have fabricated and characterized thin-film (1.74 µm) AlGaAs solar cells with and without a layer of InAs quantum dots. We show the adequacy of our method to measure at low temperatures by means of measuring the photocurrent or quantum efficiency of the devices at different temperatures, ranging from 300 K to 20 K.