Uniform and controlled Si doping of Ga₂O₃by disilane via hybrid molecular beam epitaxy

β-Ga₂O₃ has attracted a great deal of interest in recent years due to its ultra-wide bandgap (E_g = 4.7eV) and the availability of large-scale substrates. n-type doping of Ga₂O₃ has been achieved using Sn, Si, and Ge by metal-organic chemical vapor deposition (MOCVD), pulsed laser deposition (PLD), and molecular beam epitaxy (MBE). Regardless, in conventional MBE systems, achieving Si-doped Ga₂O₃ films with wide-ranging doping concentrations and uniform doping profiles has been challenging due to the oxidation of solid Si source in the oxygen-rich environment. Recently, J. P. McCandless et al. reached to low 10¹⁷ cm^-3 Si doping concentration by inserting an endplate into the Si crucible.





In this work, we propose using diluted disilane (Si₂H₆/N₂) in a hybrid MBE to obtain Si-doped Ga₂O₃. In this approach, instead of using traditional solid Si as the precursor, a gas source of Si, disilane (Si₂H₆), is introduced to avoid the oxidation of Si during the growth. By using diluted disilane, we have achieved a wide range of Si doping concentrations from low 10¹⁶ cm^-3 to 10¹⁹ cm^-3 with a uniform doping profile. The room temperature electron mobility was measured to be ~130 cm²/Vs for an electron concentration of 3 × 10¹⁷ cm^-3. Atomic force microscopy (AFM) images show smooth surface morphologies. Silicon and Hydrogen incorporation was measured using secondary ion mass spectrometry (SIMS). The hydrogen incorporation remained similar to that in unintentionally doped films. This is the first time that disilane has been successfully used for the Si-doping of Ga₂O₃ by MBE.