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

Abstract

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 Qtot/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.