Modification of Schottky barrier height using an inorganic compound interface layer for various contact metals in the metal/p-Si device structure

Abstract

In this study, lithium fluoride (LiF) was employed as an interface material by thermal evaporation technique and its effect of on basic device parameters such as Schottky barrier height and ideality factor was examined for different contact metals. In the device fabrication process, the aluminum (Al) metal was used only as the ohmic contact for all devices while Al, gold (Au), chromium (Cr) and nickel (Ni) were employed as Schottky contacts. The reference device structures were also fabricated without the LiF interfacial layers to better understand the effect of the interfacial layer. Thus, the metal/p-Si/Al and metal/LiF/p-Si/Al Schottky type device structures were obtained by using p type silicon (Si) wafer and Al, Au, Cr, Ni for top metal contacts to investigate the effect of these metals on the device parameters. The electrical measurements of the reference samples and Au/LiF/p-Si/Al, Al/LiF/p-Si/Al, Cr/LiF/p-Si/Al, Ni/LiF/p-Si/Al Schottky type diode structures were characterized by current–voltage (I–V) measurements at the room temperature and dark. Basic diode parameters such as ideality factor (n) and barrier height (Φb) of eight Schottky devices were calculated by the thermionic emission (TE) theory, Cheung and Norde functions at room temperature. The results revealed that the LiF interface material caused an increase in the barrier height (BH) compared to the reference device. This increase in the BH values of the devices in accordance with their reference samples was different for Al, Au, Cr, and Ni metals. In the calculation made by TE theory, the LiF interface increased the BH of the Al/LiF/p-Si device from 0.69 to 0.78, while increasing the BH of the Ni/ LiF/p-Si device from 0.57 to 0.65. The obtained results highlighted that the work function of Schottky metals and interface material are effective in modulating the BH of the device. In addition, I–V measurements of the AI/LiF/p-Si/Al device were taken under light and the results obtained showed that this device can be used in photodiode applications.