SCHOTTKY-BARRIER ENHANCEMENT USING REACTED NI2AL3NI/N-GAAS, NI/AL/NI/N-GAAS, AND NIAL/AL/NI/N-GAAS CONTACTS

A systematic study of the enhancement of Schottky barriers to n-GaAs has been carried out using the following diodes, Ni2Al 3/n-GaAs, Ni2Al3/Ni/n-GaAs, Ni/Al/Ni/n-GaAs and NiAl/Al/Ni/ n-GaAs, prepared by sputter deposition at a base pressure ∼2×10-7 Torr. A high Schottky barrier height ranging from 0.95 to 0.98 eV (deduced from current-voltage measurements) was observed for all the annealed contacts except for Ni2Al3/n-GaAs. Enhancement of the Schottky barrier height in all the contacts was attributed to the formation of a high Al content (Al,Ga)As layer at the metal/semiconductor interface. A regrowth mechanism was used to rationalize the Schottky barrier enhancement. In this mechanism, Ni reacts with GaAs initially at low temperatures, forming NixGaAs. The NixGaAs layer then reacts with the Ni-Al layer on top to form the (Al, Ga)As layer under subsequent high temperature annealing. A (200) dark-field XTEM image of the annealed contact was used to demonstrate the existence of this (Al,Ga)As phase. © 1995 American Institute of Physics.