Effects of Miscut Substrates on Electrical Conductivity Across InP and GaAs Wafer-Bonded Structures

Abstract

Wafer bonding of GaAs and InP using an (NH4)2S treatment are investigated for the effect of the wafer offcut angle on the electrical conductivity of wafer-bonded III-V interfaces. HRTEM and STEM are used to confirm the misorientation of the bonded samples and to compare the interface morphology across the range of relative misorientations. A line ratio at the interface shows that the 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. Fitting the zero-bias conductance over a range of temperatures reveals an increase in barrier heights for samples with greater than 4° misoriented bonded pairs. This demonstrates that the out-of-plane relative surface misorientation is a critical parameter to be monitored and thus any in-plane twist as well in order to achieve superior electrical conductivity in direct-bonded multijunction solar applications.