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Published May 1, 2008 | public
Journal Article Open

Improved electrical properties of wafer-bonded p-GaAs/n-InP interfaces with sulfide passivation


Sulfide-passivated GaAs and InP wafers were directly bonded to explore the efficiency of sulfide passivation on the bonded interfacial properties. We find that the bonded GaAs/InP interfaces after sulfide passivation contain sulfur atoms and a decreased amount of oxide species relative to the pairs bonded after conventional acid treatment; however, the residual sulfur atoms have no effect on the bonding strength. The electrical properties of the bonded p-GaAs/n-InP heterojunctions were studied for different acceptor concentrations in p-GaAs. A reduced interfacial trap state density enhances the tunnel current flow across the depletion layer in the sulfide-passivated case. A directly bonded tunnel diode with a heavily doped p-GaAs/n-InP heterojunction was achieved when the wafers were sulfide passivated and then bonded at temperatures as low as 300 °C. This sulfide-passivated tunnel diode can be used for fabrication of lattice-mismatched multijunction solar cells in which subcells are integrated via direct bonding.

Additional Information

© 2008 American Institute of Physics. Received 10 December 2007; accepted 27 February 2008; published 2 May 2008. This work was supported by the National Renewable Energy Laboratory (NREL). We also acknowledge support from the Center for Science and Engineering of Materials (CSEM), a NSF Materials Research Science and Engineering Center at Caltech, for use of their facilities. Helpful discussions with M.J. Archer is gratefully acknowledged.


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