Studies of advanced structures based on Gallium Nitride (GaN) – STARGAN

Nowadays, AlGaN/GaN HEMTs are certainly the most III-V device studied component mainly for microwave power applications. This research thematic is highly competitive with American and Japanese laboratories, such as CREE, NITRONEX, TOSHIBA, EUDYNA etc …
GaN technology has been steadily improved and each year HEMTs with new RF record performance have been reported mainly on SiC substrate.
The activity proposed in STARGAN project is a new trend in the gallium nitride world community. The STARGAN consortium intends to perform bandgap engineering of AlGaN/GaN structures grown on silicon substrate in order to develop a new low cost epitaxy well suited for the fabrication of transistors working in mm-wave range. Up to now, only few researches were performed in this field, mainly up to 18GHz.
STARGAN is a prospective program in which is realized in a real integrated and concerted way the convergence between the epilayer and the technological process. In order to achieve the goal of working at mm-wave frequencies, new advanced epitaxial stacks and process technologies will be investigated. The impact of different parameters on the device performances will be studied and the transistor will be analyzed as a whole by physical and reliability measurements. The originality of the STARGAN project concerns innovation based on varying the nature of the epitaxy grown by Molecular Beam Epitaxy (MBE) on silicon substrate in adequacy with adjusted processing steps. The objective consists to find the best compromise in order to get high sheet carrier density associated to high carrier mobility and good buffer isolation. When, the layer structure, the epitaxial growth conditions and the technological process will be optimized, reliability testing will be performed based on high temperature accelerated life testing. The final goal consists to get performances well suited for further industrial fabrication of MMICs working up to 40GHz.