The technology of RF communications systems has experienced a phenomenal progress in the last decades. Gallium nitride (GaN) has been identified as the semiconductor that will take over after silicon (Si) to meet the needs of the increasingly market requests. This is explained by the physical parameters of this new material, which highly exceed those of Si. The objective of this project is the development of an enhancement and depletion modes HEMT-GaN based technologies suitable for the manufacturing of MMIC circuits operating at high frequency. This project is divided in 3 research axes: 1) GaN based MMIC fabrication process, including epitaxy, 2) device characterization and modeling, 3) circuit design and characterization. The consortium gathers 3 research laboratories and 1 industrial company covering a very wide range of skills and applied knowledge. The different partners are complementary and expert in the field of GaN activities, which is a major key that will lead to the success of this project. In Sky-GaN project, the development of short gate length GaN-HEMT process will be used to fabricate a prototype Power Amplifier (PA) MMIC circuits to validate these new developed technologies. Indeed, the optimized micro-fabrication process that will be developed will allow the production of new custom PA circuit with higher performance in frequency band covering the E-band [71-76] GHz and [81-86] GHz for both technologies. These fabricated prototypes will also be used as demonstration samples to support the development of new business opportunities for the industrial partner, creating new job opportunities for young researchers and highly qualifier professional. On the other hand, for the academic laboratories participating to Sky-dream project, the research and development work will produce important scientific impact and economic value, which is in complete agreement with the mission of CNRS.