Pre-atomic layer deposition surface cleaning and chemical passivation of (100) In0.2Ga0.8As and deposition of ultrathin Al2O3 gate insulators

Abstract
We have developed and tested the efficacy of a method for pre-atomic layer deposition (ALD)surface preparation that removes native oxides from the (100) In 0.2 Ga 0.8 As surface and provides a clean starting surface for ALD of ultrathin Al 2 O 3 layers. Successive wet etching by aqueous HCl and N H 4 ( O H ) solutions and in situ pre-ALD thermal desorption of residual elemental As were performed. Photoelectron spectra obtained after ALD of Al 2 O 3 on In 0.2 Ga 0.8 As prepared by this method revealed that the interface was free of In, Ga, and As oxides. The resultant metal-oxide-semiconductor capacitors with Pt electrodes exhibited capacitance-derived equivalent oxide thicknesses as small as 1.8 nm .