Thin film transistors have recently received increasing interest both for conventional logic applications as well as emerging neuromorphic computation schemes. Thin film transistors are flexible devices that do not require single crystal semiconductor wafers and can therefore be integrated in many places in a chip where conventional Si-based transistors cannot, including the stacked integration in the interconnect systems above the Si-based CMOS circuits. Especially amorphous or polycrystalline semiconducting oxides are highly promising materials for thin film transistors since they combine comparatively high mobilities, much higher than for example amorphous Si, with large band gaps and thus low off-state currents in the transistors.
Prominent examples of such a semiconducting oxide is indium gallium zinc oxide (IGZO) or zinc tin oxide (ZTO), which have been used commercially in displays. A major drawback of oxide thin film transistors is however, the most promising materials (including IGZO and ZTO) are all n-type semiconductors without the possibility for p-type doping. While p-type oxide semiconductors, such as SnO, have been reported, their mobilities are still much lower than their n-type counterparts. This currently impedes the usage of such materials in high performance logic CMOS circuits.
The goal of this PhD thesis will be the study of p-type oxide semiconductors. In a first step, thin films will be deposited by pulsed laser deposition on relevant Si-based substrates. The films will then be characterized using structural (XRD, XRR), optical (ellipsometry), and electrical (sheet resistance, Hall effect) techniques. The final goal of this study is to develop thin film transistors based on promising p-type materials in collaboration with the TFT device group at imec. The characterization results will be correlated to deposition parameters with the aim to optimize the thin film properties, especially the hole mobility.
The student will learn to use state-of-the art equipment to deposit and characterize thin films of oxide semiconductors. He or she will additionally learn about the material science of oxide semiconductors and thin film transistors. A background in materials science, chemistry, (applied) physics, or nanotechnology is ideal, together with an interest in thin film deposition and characterization of advanced materials.
Required background: Materials Science/Engineering, Chemistry, Nanotechnology, Applied Physics, Physics
Type of work: 70% experimental, 20% data analysis, 10% literature study
Supervisor: Annelies Delabie
Daily advisor: Christoph Adelmann, Sean McMitchell
The reference code for this position is 2020-008. Mention this reference code on your application form.
Chinese nationals who wish to apply for the CSC scholarship, should use the following code when applying for this topic: CSC2020-05.