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FIZIKA A 5 (1996) 2, 55-61
 
AlNiGe AS A NEW DEDICATED MATERIAL FOR CONTACTS TO n-GaAs
LAJOS DÁVID, BALÁZS KOVÁCSa, BÉLA PÉCZb, IMRE
MOJZESa, LÁSZLÓ DOBOSb and GYULA VINCZEb
Kandó Kálmán Polytechnic, Institute of Microelectronics and Technology, H-1084
Budapest, Tavaszmezö u. 17., Hungary
a Technical University of Budapest, Department of Electronics Technology,
H-1521 Budapest, Hungary
b Research Institute for Technical Physics of the Hungarian Academy of
Sciences, H-1325 Budapest, P. O. Box 76, Hungary
Received 7 April 1995
Revised manuscript received 28 May 1996
Al(150 nm)/Ni(30 nm)/Ge(40 nm) layers have been deposited onto n-type GaAs by thermal
evaporation. The samples have been annealed for 20 minutes in flowing forming gas H2:N2
(30%:70%). The alloying behaviour of the specimens has been investigated by electron
microscope. The contacts show a bilayer structure in the case of as-deposited samples. The
top layer is pure Al and the second one is Ni-Ge. The metal-semiconductor interface is
sharp. Annealing at 400 °C resulted in the
formation of florets on the surface assumed to be AlGe eutectic; meanwhile, randomly
distributed pits of size 10 nm have been grown into the GaAs. The samples annealed at 450 °C show bilayer structure. The top layer is pure Ge and the
second one consists of Al-Ni(Ge). On samples annealed at 500 °C
thick alloyed layer has been found with deep pyramidal pits of size 0.25 mm. The interface region between GaAs and the pits contains
substantial amount of Al. Contrary to the published results, I-V (current-voltage)
characteristics of the annealed specimens show that the contacts remained rectifying at
each applied annealing process. The temperature dependence of parameters evaluated from
either current-voltage or capacitance-voltage characteristics prove that the
characteristic form of conductance is the anomalous thermionic-field emission.
UDC 538.971
PACS 79.40.+z
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