Characterization of enhancement-mode n-channel sulfur-treated InP MOSFET with Al2O3/TiO2 gate oxides prepared by atomic layer deposition

• Al2O3/TiO2 prepared by ALD was grown on (NH4)2S treated InP.
• The leakage currents can reach 1.9 × 10−8 and 1.1 × 10−6 A/cm2 at ±2 MV/cm.
• The lowest interface state density is 5.7 × 1011 cm−2 eV−1.
• Enhancement-mode n-channel InP MOSFET with ALD–Al2O3/TiO2 gate oxides was fabricated.
• The MOSFET shows a gm of 135 mS/mm and electron channel mobility of 275 cm2/V s.

Polycrystalline TiO2 film with the thickness of 4 nm prepared by atomic layer deposition (ALD) on ammonium sulfide treated p-type InP shows a good interface quality but with slightly higher leakage current mainly resulted from the thermionic emission and grain boundary. Stacked with a high band-gap amorphous Al2O3 of 3 nm prepared by atomic layer deposition on TiO2, the leakage currents are improved to 1.9 × 10−8 and 1.1 × 10−6 A/cm2 at ±2 MV/cm. The equivalent dielectric constant of Al2O3/TiO2 is about 18. The lowest interface state density is around 5.7 × 1011 cm−2 eV−1. The fabricated enhancement-mode n-channel sulfur-treated InP MOSFET exhibits good electrical characteristics with a maximum transconductance of 135 mS/mm and electron channel mobility of 275 cm2/V s.