Electrical Conductivity of Direct Wafer-Bonded GaAs/GaAs Structures for Wafer-Bonded Tandem Solar Cells

Abstract

Wafer bonding of GaAs using an ammonium sulfide (NH4)2S treatment is investigated for various structures. The effect of the wafer offcut angle on the electrical conductivity of III-V solar cell devices using n-GaAs/n-GaAs wafer-bonded structures is studied. High resolution x-ray diffraction is used to confirm the misorientation of the bonded samples. Additionally, we compare the electrical properties of epitaxially grown p-n junctions on GaAs to n-GaAs/p-GaAs wafer-bonded structures. High resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM) are used to compare the interface morphology across the range of relative misorientations after a 600 {degree sign}C RTP. The ratio of well-bonded crystalline regions to amorphous oxide inclusions is consistent across all bonded samples, indicating that the degree of misorientation does not affect the level of interface recrystallization at high temperatures.