PhD thesis supervisor: dr. Linas Ardaravičius (apply for recommendation)
Carrier transport in CVD graphene field-effect transistors at high electric fields
Graphene theme is actual since 2004 when it was succesfully exfoliated from graphite. Various methods to obtain graphene have appeared and one of them is the chemical vapor deposited (CVD) graphene on Cu. Then it is wet or dry transferred on dielectric (usually SiO2). SiO2 can be grown on isolating Si substrate and is conductive (p-type) when back-gated field effect transistors are formed. During doctoral studies TLM patterns will be formed on graphene with evaporated Ti/Au contacts. The contact resistance will be estimated from TLM resistance measurements. DC and pulsed current (10 ns-1 µs) measurements will performed on TLM patterns. Graphene field-effect mobility will be estimated from transistor transfer characteristics. Additionally, carrier density will be estimated from the graphene resistance measurements and channel geometry. Nanosecond-pulsed current technique is a perspective graphene transport characterization tool. Joule heat in the graphene channel can be minimized and higher current values and stronger electric fields can be attained. Carrier drift velocity dependence on the electric field will be estimated from measured current density. Maximum carrier drift velocity in graphene – one of the key transport parameters - is used to determine current gain cutoff frequency in graphene transistor and defines the speed of the device.