Laterally Inhomogeneous Barrier Height Analysis for Thermally Annealed CuNiTi/<i>p</i>-InP Contacts

Abstract

The fabrication of thermally stable Schottky contacts with high barrier height (BH) to InP is one of the main challenges for InP-based device technology. CuNiTi/p-InP Schottky barrier diodes (SBDs) (25 dots) on p-InP substrate were fabricated by conventional vacuum deposition. Characteristic parameters such as BH and ideality factor (n) of as-deposited and annealed CuNiTi/p-InP diodes have been computed by thermionic emission (TE) theory from the forward-bias current-voltage (I-V) data, at room temperature and in dark. The value of BH and n varies from 0.452 to 0.631 eV and 1.172 to 2.815, respectively for the as-deposited SBDs. The results showed that characteristic parameters of CuNiTi/p-InP structures differ from one device to another even though they were identically prepared. Hence, to overcome these problems post thermal annealing was implemented since the annealing process can improve the interfacial quality as well as can induce a recrystallization of the gate metals. BH values for CuNiTi/p-InP SBDs have also varied from 0.765 to 0.804 eV, and ideality factor n from 1.161 to 1.253 after annealing at 500 °C for two minutes. As a result of the thermal annealing, it has been seen that the BH values of the annealed SBDs are larger than those of the as-deposited ones. A statistical study on the diode parameters has been made. The experimental BH and ideality factor distributions were fitted by a Gaussian distribution (GD) function. Lateral homogeneous BH (φhom.) values of 0.628 eV and 0.886 eV for the as-deposited and annealed CuNiTi/p-InP SBDs has been obtained from the φeff.-n plots by using Tung’s lateral inhomogeneity approach. An increment of 0.258 eV in the BH for the 500 °C annealing devices with respect to that of the as-deposited ones has been ascribed to the formation of the positively charged interface defects that electrically actives in the metal-semiconductor (MS) interface.