GaN based diodes for tunable microwave circuits

Context:

For microwave devices, reconfigurability permits to modify at least one electrical characteristic of the circuit using integrated components or a functional materials. The aim is to use the same system for numerous applications or to give the ability to adapt to the environment. The purpose of this thesis is the realization of the Gallium Nitride (GaN) based component to obtain the tunability of microwave circuits. GaN is already used for high power applications at high frequency but not for the tunability. The major interest to develop GaN tunable devices is to integrate on the same substrate, ie monolithically, the tunable part (to obtain agility) and the amplification part (to obtain high power) of a microwave front-end.

Projet:

In this thesis, two types of components will be investigated, PIN diodes (Positive Intrinsic Negative) and varicap diodes (variable capacitor). Main differences between these two types of diodes is that PIN diodes can be assimilated to variable resistors and thus allows to realize switches to choose a path for the signal, its working principle is thus qauntified. Varicap diodes, can be assimilated to variable capacitors and thus permits to realize circuit with continuously variable characteristics. In order to realize those kind of diodes, some challenge need to be overcome, especially the realization of low losses ohmic contact on p-type GaN. This thesis will firstly focus of the optimization of the ohmic contact on GaN and the characterization of the interfaces between the different layers of the stack-up, using conventional tools (SEM, AFM, electrical measurements). Then, using the optimal conditions of ohmic contact deposition, fabrication and measurement of GaN based diodes up to several GHz will be done.

Candidate profile:

You have a good knowledge of semiconductor physics and/or microelectronics. An experience in clean room or material synthesis would be appreciated.

Place: At the GREMAN laboratory, on the CERTeM platform.. 16 rue Pierre et Marie Curie, 37100 TOURS, FRANCE. Tours is located at 230 km south from Paris.

Application:

kevin.nadaud@univ-tours.fr, jerome.billoue@univ-tours.fr et daniel.alquier@univ-tours.fr

Website: http://greman.univ-tours.fr/