PhD position on preparation and characterization of Ga2O3-diamond heterostructure UV photodetectors

One of the most significant challenges of the recent years, related to the development of new electronic devices and having potential for major improvement of the current status in a vast variety of human activities can be found in the field of solar-blind (SB) ultraviolet (UV) photodetectors (PDs). Novel UV PDs, especially for deep-UV (DUV) optoelectronics (wavelengths shorter than 280 nm) are needed. These cannot typically be manufactured from conventional materials. This resulted in the development of ultrawide bandgap (UWBG) semiconductors (such as Al_xGa_1−xN, hBN, Ga₂O₃, and diamond) and their utilisation for SB UV PDs. Gallium oxide (Ga₂O₃), a naturally n-type semiconductor, represents a suitable UWBG material, showing a very good potential and capability to significantly improve the current state-of-the-art electronic devices. Furthermore, synthetic diamond has gained a strong reputation to be an exceptionally versatile material due to its attractive physical and chemical properties and availability of facile preparation of films with p-type conduction. On the other hand, it is very difficult to prepare p-type Ga₂O₃ and n-type diamond.

In this work, we will target the development and detailed characterisation of new high-performance DUV SB PDs with p-n or p-i-n device structure, comprising n- and i-type Ga₂O₃ and p-type diamond. Such heterostructure devices represent a favourable solution combining the best of the two UWBG worlds. The Ga₂O₃ layers will be grown by liquid-injection metal-organic chemical vapour deposition (LI-MOCVD), a growth technique developed at IEE SAS. Polycrystalline diamond films will be prepared by MW plasma-enhanced CVD method in close cooperation with the Institute of Physics of the Czech Academy of Sciences in Prague. UV PDs and other electronic devices will be fabricated using modern techniques and tools available at the IEE SAS, i.e. optical or electron-beam lithography, reactive ion etching, and thin films deposition. The designed periodic structures, electric contacts, interdigitated arrays, and van der Pauw test structures will be prepared using a metallic mask prepared by the vacuum sputtering or evaporation through lithographically-prepared masks and patterned by a lift-off process.

The main goal of this PhD thesis is the fabrication, characterisation, and deep understanding of the effects at the Ga₂O₃-diamond heterostructure interface, and to assess their influence on the properties of such a heterojunction. In addition, focus will be also on testing of the properties of prepared UV photodetectors and their radiation hardness when exposed to the ionising radiation.

For further information about the scientific content please contact the supervisor: Dr. Marián Varga, marian.varga@savba.sk