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 (Ga<inf>2</inf>O<inf>3</inf>) 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 J<inf>0</inf> of 7 fA cm-2 is extracted. From high frequency capacitance-voltage (HF CV) measurements it is shown that, as in the case of Al<inf>2</inf>O<inf>3</inf>, the presence of a high negative charge density Q<inf>tot</inf>/q of up to -6.2 × 1012 cm-2 is one factor contributing to the passivation of silicon by Ga<inf>2</inf>O<inf>3</inf>. 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 H<inf>2</inf>/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 J<inf>0</inf> of 52 fA cm-2. Show more