Optimization of electrostatic seeding technique for wafer-scale diamond fabrication on β-Ga2O3

Abstract

Integrating diamonds with β-Ga2O3 is a promising solution for addressing the problem of poor thermal conductivity and limited p-type dopability of β-Ga2O3. However, growing diamonds on β-Ga2O3 is challenging, especially without any interfacial layer, and achieving large-scale uniform diamond films is also tricky. This paper explores the vital role of an electrostatic seeding technique involving the use of Polydiallyldimethylammonium chloride (PDDAC) polymer with a positive zeta potential and diamond nano slurries with a negative zeta potential to facilitate the integration of diamond with β-Ga2O3. We conduct a detailed analysis of each step of this seeding technique, adjusting the spinning speed of the polymer coating, spinning period, baking period, and ultrasonication period to understand the underlying mechanisms preventing large-scale diamond growth and to identify strategies for achieving wafer-scale diamond fabrication on single crystal β-Ga2O3 film. This process facilitates the attainment of a uniform dispersion of diamond nanoparticles on β-Ga2O3 at a seeding density of ∼1.82 × 1011 cm−2. The optimized seeding technique has enabled the successful growth of wafer-scale diamond films on β-Ga2O3, as confirmed by scanning electron microscopy (SEM). Additionally, the high quality of the diamond film is affirmed by a quality factor of 96.75 % and a narrow full-width half maximum of 10.28 cm−1 in the T2g peak of the Raman spectra. The X-ray diffraction pattern reinforces the excellent quality of polycrystalline diamond films with minimum stress. In summary, this research provides valuable insights into the polymer-assisted electrostatic seeding technique, paving the way for the uniform growth of wafer-scale diamond films on β-Ga2O3, which is critical for realizing β-Ga2O3-based heterostructure devices.