Examination by interfacial layer and inhomogeneous barrier height model of temperature-dependent I-V characteristics in Co/p-InP contacts

Abstract

The current-voltage (I-V) characteristics of the sputtered Co/p-InP Schottky diodes have been measured in the temperature range of 80-400 K with steps of 20 K. It has been seen that the I-V characteristics of the device cannot be explained by the classical thermionic emission theory due to the ideality factor values larger than unity, 2.01 at 300 K and 1.73 at 400 K which indicate the presence of a native oxide layer at the metal/semiconductor interface. Therefore, the I-V characteristics have been corrected for the effect of the native oxide layer with a transmission coefficient of θp = 1.76 × 10-3. The fact that the ideality factor and barrier height (BH) values have changed by change of the sample temperature has been attributed to the presence of the lateral inhomogeneities of the BH. Before correcting for the effect of the native oxide layer, the BH inhomogeneity has obeyed the double-Gaussian distribution (GD) model of BHs suggested in refs. [Y.L. Jiang, G.P. Ru, F. Lu, X.-P. Qu, B.Z. Li, W. Li, A.Z. Li, Chin. Phys. Lett. 19 (2002) 553; Y.L. Jiang, G.P. Ru, F. Lu, P.X. Qu, B.Z. Li, S. Young, J. Appl. Phys. 93 (2003) 866; S. Huang, F. Lu, Appl. Surf. Sci. 252 (2006) 4027] which assumes the simultaneous existence of two GDs of BHs. After correcting, the BH inhomogeneity has obeyed the single-GD model of BHs suggested by some authors, which fits to a straight line in the temperature range of 80-400 K. Thus, after correcting, a Richardson constant value of 76.45 A/cm2 K2, which is close agreement with the value of 60 A/cm2 K2 known for p-type InP, has been obtained from the modified ln(I0C/T2) - q2σ2/(2k2T2) versus 1/T plotted by the single-GD of the BHs. © 2009 Elsevier B.V. All rights reserved.