Density functional theory simulations of amorphous high-κ oxides on a compound semiconductor alloy: a-Al2O3/InGaAs(100)-(4×2), a-HfO2/InGaAs(100)-(4×2), and a-ZrO2/InGaAs(100)-(4×2)

Low temperature thermal ALD of a SiNx interfacial diffusion barrier and interface passivation layer on SixGe1- x(001) and SixGe1- x(110)

Atomic layer deposition of a silicon rich SiN_x layer on Si_0.7Ge_0.3(001), Si_0.5Ge_0.5(001), and Si_0.5Ge_0.5(110) surfaces has been achieved by sequential pulsing of Si₂Cl₆ and N₂H₄ precursors at a substrate temperature of 285 °C. XPS spectra show a higher binding energy shoulder peak on Si 2p indicative of SiO_xN_yCl_z bonding while Ge 2p and Ge 3d peaks show only a small amount of higher binding energy components consistent with only interfacial bonds, indicating the growth of SiO_xN_y on the SiGe surface with negligible subsurface reactions. Scanning tunneling spectroscopy measurements confirm that the SiN_x interfacial layer forms an electrically passive surface on p-type Si_0.70Ge_0.30(001), Si_0.50Ge_0.50(110), and Si_0.50Ge_0.50(001) substrates as the surface Fermi level is unpinned and the electronic structure is free of states in the band gap. DFT calculations show that a Si rich a-SiO_0.4N_0,4 interlayer can produce lower interfacial defect density than stoichiometric a-SiO_0.8N_0.8, substoichiometric a-Si₃N₂, or stoichiometric a-Si₃N₄ interlayers by minimizing strain and bond breaking in the SiGe by the interlayer. Metal-oxide-semiconductor capacitors devices were fabricated on p-type Si_0.7Ge_0.3(001) and Si_0.5Ge_0.5(001) substrates with and without the insertion of an ALD SiO_xN_y interfacial layer, and the SiO_xN_y layer resulted in a decrease in interface state density near midgap with a comparable C_max value.

Density-Functional Theory Molecular Dynamics Simulations and Experimental Characterization of a-Al₂O₃/SiGe Interfaces

Density-functional theory molecular dynamics simulations were employed to investigate direct interfaces between a-Al2O3 and Si0.50Ge0.50 with Si- and Ge-terminations. The simulated stacks revealed mixed interfacial bonding. While Si-O and Ge-O bonds are unlikely to be problematic, bonding between Al and Si or Ge could result in metallic bond formation; however, the internal bonds of a-Al2O3 are sufficiently strong to allow just weak Al bonding to the SiGe surface thereby preventing formation of metallic-like states but leave dangling bonds. The oxide/SiGe band gaps were unpinned and close to the SiGe bulk band gap. The interfaces had SiGe dangling bonds, but they were sufficiently filled that they did not produce midgap states. Capacitance-voltage (C-V) spectroscopy and angle-resolved X-ray photoelectron spectroscopy experimentally confirmed formation of interfaces with low interface trap density via direct bonding between a-Al2O3 and SiGe.