The Effect of Interfacial Dipoles on the Metal-Double Interlayers-Semiconductor Structure and Their Application in Contact Resistivity Reduction

Abstract

We demonstrate the contact resistance reduction for III-V semiconductor-based electrical and optical devices using the interfacial dipole effect of ultrathin double interlayers in a metal-interlayers-semiconductor (M-I-S) structure. An M-I-S structure blocks metal-induced gap states (MIGS) to a sufficient degree to alleviate Fermi level pinning caused by MIGS, resulting in contact resistance reduction. In addition, the ZnO/TiO interlayers of an M-I-S structure induce an interfacial dipole effect that produces Schottky barrier height (Φ) reduction, which reduces the specific contact resistivity (ρ) of the metal/n-type III-V semiconductor contact. As a result, the Ti/ZnO(0.5 nm)/TiO(0.5 nm)/n-GaAs metal-double interlayers-semiconductor (M-DI-S) structure achieved a ρ of 2.51 × 10 Ω·cm, which exhibited an ∼42 000× reduction and an ∼40× reduction compared to the Ti/n-GaAs metal-semiconductor (M-S) contact and the Ti/TiO(0.5 nm)/n-GaAs M-I-S structure, respectively. The interfacial dipole at the ZnO/TiO interface was determined to be approximately -0.104 eV, which induced a decrease in the effective work function of Ti and, therefore, reduced Φ. X-ray photoelectron spectroscopy analysis of the M-DI-S structure also confirmed the existence of the interfacial dipole. On the basis of these results, the M-DI-S structure offers a promising nonalloyed Ohmic contact scheme for the development of III-V semiconductor-based applications.

Schottky Barrier Height Engineering for Electrical Contacts of Multilayered MoS2 Transistors with Reduction of Metal-Induced Gap States

“…Mechanism of SBH Control: Fermi-Level Unpinning by MIGS Reduction. The SBH control by insertion of the interlayer can be explained by three mechanisms: (1) Fermilevel unpinning by the MIGS reduction, [23][24][25][26][27][28][29][30][31][32]35,36 (2) Fermilevel unpinning by the metal/semiconductor interface passivation, 27,28,44 and (3) interface dipole formation. 23,26,33,34,36 First, the two Fermi-level unpinning effects and the interface dipole effect can be separated from the SBH vs contact metal work function plot as shown in Figure 6a.…”

“…The SBH control by insertion of the interlayer can be explained by three mechanisms: (1) Fermi-level unpinning by the MIGS reduction, − ,, (2) Fermi-level unpinning by the metal/semiconductor interface passivation, ,, and (3) interface dipole formation. ,,,, First, the two Fermi-level unpinning effects and the interface dipole effect can be separated from the SBH vs contact metal work function plot as shown in Figure a. In the plot, the intersection point between the ideal line with S = 1 and the experimentally obtained MS line with S = 0.02 is a branch point that does not change as the pinning factor changes.…”

“…These MIGS have been identified as the main cause of the FLP in conventional semiconductor materials. Therefore, a metal–interlayer–semiconductor (MIS) structure has been developed to alleviate the FLP and reduce the electron SBH by reducing the MIGS in Si, , Ge, − and III–V. − Ultrathin interlayers such as TiO 2 − ,,, and ZnO − ,, which exhibit a small conduction band offset (CBO) to semiconductor materials are inserted between the metal contact and the semiconductor as the Fermi-level unpinning layer that minimizes the increase in the interlayer resistance. Several researchers have previously developed the MIS structure for the MoS 2 to control the electron SBH of its electrical contacts by using Ta 2 O 5 , TiO 2 , − MgO, and h -BN , interlayers.…”

“…In this work, the SBH controllability is improved by using an MIS structure on multilayered MoS 2 FETs, and its SBH controlling mechanism is systematically investigated by analyzing three possible mechanisms: (1) Fermi-level unpinning by the MIGS reduction, − ,, (2) Fermi-level unpinning by the metal/semiconductor interface passivation, ,, and (3) interface dipole formation. ,,,, Four metals with various work-function values, titanium (Ti), copper (Cu), gold (Au), and platinum (Pt), are adopted as contact metals with an ultrathin titanium dioxide (TiO 2 ) interlayer, and the transfer characteristics of multilayered MoS 2 FETs and SBH of their S/D contacts are analyzed to demonstrate the SBH-controlling effect. The mechanism of the SBH control is investigated by comparing each of the three possible mechanisms.…”

Controllable Electrical Contact Resistance between Cu and Oriented-Bi2Te3 Film via Interface Tuning

“…The M–S contact resistance is affected by several factors including the work function of both materials, interfacial states, crystal structure, and so on . The methods of surface or interface treatment, , metallization system design, , and heavy doping by ion implantation are commonly adopted to mitigate contact resistance. For instance, Gupta et al acquired quite low contact resistivity of approximately 10 –7 Ω cm 2 via surface treatment and post deposition annealing in the study of Bi 2 Te 3 –Ni/Co contacts.…”