Fabrication and electrical characteristics of TFTs based on chemically deposited CdS films, using glycine as a complexing agent

Abstract

In this work, we report on the fabrication and electrical characteristics of thin film transistors (TFTs) using chemically deposited cadmium sulfide (CdS) thin films as the semiconductor active layer in back-gated devices. The CdS thin films were deposited by the chemical bath deposition (CBD) technique using glycine as the complexing agent. The CdS layers were deposited on SiO2/Si-n substrates and lift-off was used to define the source and drain contacts (Au) on top of these layers. The Si-n wafer with a chromium-gold back contact served as the common gate for the transistors. Several devices with different channel lengths ranging from 10 to 80 µm were fabricated by this process. We studied the properties of the CdS layers deposited by this glycine-based CBD process and the electrical behavior of the transistors as a function of the channel length. The experimental results show that as-deposited CdS are n-type in character and devices exhibit typical pinch-off in drain current versus source–drain voltage (IDS–VDS) curves for several gate voltages. The values of the threshold voltage of the devices were in the range from 8.5 to 8.9 V, depending on the channel length. Channel mobility was between 4.3 and 5.2 cm2 V−1 s−1. This research implies that CdS TFTs produced by a simple and low-cost technique could be applicable to electronic devices.