p-Doping Engineering of AlGaN Materials – DOPALGAN

Gallium nitride (GaN) semiconductors are now widely used in daily life applications (lighting, chargers…). Wider band gap aluminium gallium nitride (AlGaN) semiconductors are now emerging to push forward the performances and/or open new application fields in strategic markets (medical, environment, communication...).
The success story of GaN was only completed with the control of conductive p-type layers. Yet, it still remains to be achieved for AlGaN alloys, and we propose to tackle this major issue in DOPALGAN. The originality of our proposal is to combine and develop innovative technologies and materials dedicated to molecular beam epitaxy (MBE) processes in order to obtain AlGaN layers with hole concentrations above 1e18 cm-3. Efficient p-type doping requires to find solutions to overcome: 1) High activation energies found for the currently used Mg-doping; 2) Low acceptor solubility limits; 3) The formation of self-compensating point defects (SCD). We will address these points by developing technological and scientific solutions through:
1) An in-depth understanding of SCD formation mechanisms; 2) The suppression of SCD ([defects] < 1e17 cm-3) by developing a new MBE technology by light excitation of the surface; 3) New epitaxial routes including the dopant source (Be, Mg), the growth technique (eg. Metal modulated epitaxy, non-equilibrium hole doping) and the nitrogen source.
The originality of the objectives is related to the development of new fabrication methods and equipment dedicated to the fabrication of a strategic family of alloys. The methodology is based on complementary skills of the consortium in the domains of epitaxial growth, optical and electronic transport, and MBE component technology. It will take its strength in the combination of high-level fabrication and characterization equipment, including the first MBE 49 multi-wafer GaN reactor installed by RIBER in CRHEA as well as the deep UV spectroscopy platform developed in L2C.