EFFECT OF THERMAL ANNEALING IN NITROGEN ON THE I-V AND C-V CHARACTERISTICS OF CR-NI-CO ALLOY LEC N-GAAS SCHOTTKY DIODES/

The Schottky barrier height Phi(b) and ideality factor n of Cr-Ni-Co a lloy Schottky contacts on an n-LEC GaAs substrate have been measured u sing current-voltage (I-V) and capacitance-voltage (C-V) techniques af ter different thermal annealings for 5 min in N-2 (temperature range f rom 300 to 600 degrees C), The values of Phi(b) and n for the forward I-V characteristics range from 0.65 and 1.001 eV at room temperature ( RT) to 0.86 and 1.095 eV at 400 degrees C. Thereby, the barrier height enhancement has been explained in terms of the presence of microclust ers of one or more interface phases produced by reactions between the alloy and GaAs or the native oxide layer. The stability value of 1.010 for n from the RT to 300 degrees C annealing has been ascribed to red uction of the native oxide layer on the GaAs surface by Cr in the allo y. The C-V relationship of the Cr-Ni-Co/n-GaAs Schottky diode at 1 MHz gives values of 0.68, 0.74 and 0.85 eV for Phi(b) at RT, 100 degrees C and 200 degrees C annealing temperatures respectively The fact that the C-2-V curves after annealing above 200 degrees C show two linear r egions separated by a transition segment has been attributed to the di ffusion of Cr into GaAs during the thermal annealing process.