Simplified Surface Preparation for GaAs Passivation Using Atomic Layer-Deposited High- κ Dielectrics

Atomic layer deposition (ALD) provides a unique opportunity to integrate high-quality gate dielectrics on III-V compound semiconductors. The physics and chemistry of a III-V compound semiconductor surface or interface are problems so complex that even after three decades research understanding is still limited. We report a simplified surface preparation process using ammonium hydroxide (NH₄OH) to remove the native oxide and make the hydroxylated GaAs surface ready for ALD Al₂O₃ surface chemistry. The effectiveness of GaAs passivation with ALD is demonstrated with small hysteresis, 1%-2% frequency dispersion per decade at accumulation capacitance, and a mid-bandgap D _it of 8 times10¹¹ to 1times 10¹² cm^-2 ldr eV^-1determined by the Terman method. The results from ammonium sulfide [(NH₄)₂S-,and hydrofluoric acid (HF)-, and hydrochloric acid (HCl)-treated surfaces and a surface with native oxide are also presented to compare with the results from the ammonium-hydroxide-treated surface. Fermi-level unpinning is also easily demonstrated on the ALD HfO₂ and p-type GaAs interface.