Plasma enhanced atomic layer deposition of gallium oxide on crystalline silicon: Demonstration of surface passivation and negative interfacial charge

Herein we report on the passivation of crystalline silicon by gallium oxide (Ga₂O₃) using oxygen plasma as the oxidizing reactant in an atomic layer deposition (ALD) process. Excess carrier lifetimes of 2.1 ms have been measured on 1.75 Ω cm p-type silicon, from which a surface recombination current density J₀ of 7 fA cm^-2 is extracted. From high frequency capacitance-voltage (HF CV) measurements it is shown that, as in the case of Al₂O₃, the presence of a high negative charge density Q_tot/q of up to -6.2 × 10¹² cm^-2 is one factor contributing to the passivation of silicon by Ga₂O₃. Defect densities at midgap on the order of ∼5 × 10¹¹ eV^-1 cm^-2 are extracted from the HF CV data on samples annealed at 300 °C for 30 minutes in a H₂/Ar ambient, representing an order of magnitude reduction in the defect density compared to pre-anneal data. Passivation of a boron-diffused p⁺ surface (96 Ω/□) is also demonstrated, resulting in a J₀ of 52 fA cm^-2.