Thermal stability of HfO2 high-k gate dielectric on GaAs is investigated. Compared to HfO2 gate dielectric, significant improvements in interfacial properties as well as electrical characteristics were found by constructing a Al2O3/HfO2/Al2O3 dielectric stack. At elevated temperatures, the amorphous Al2O3 layers were effective in inhibiting crystallization of HfO2. Since the passivating Al2O3 layers prevent interfacial oxide and trap charge formation, it aids in reducing the increasing rate of equivalent oxide thickness as well as capacitance-voltage hysteresis. Transmission electron microscopy and x-ray photoelectron spectroscopy data supported the improved electrical characteristic of GaAs metal-oxide-semiconductor capacitors with Al2O3/HfO2/Al2O3 gate dielectric stack.

A novel technique for the selective photochemical synthesis of silver (Ag) nanoparticles (NPs) on ZnO nanorod arrays is established by combining ultraviolet-assisted nanoimprint lithography (UV-NIL) for the definition of growth sites, hydrothermal reaction for the position-controlled growth of ZnO nanorods, and photochemical reduction for the decoration of Ag NPs on the ZnO nanorods. During photochemical reduction, the size distribution and loading of Ag NPs on ZnO nanorods can be tuned by varying the UV-irradiation time. The photochemical reduction is hypothesized to facilitate the adsorbed citrate ions on the surface of ZnO, allowing Ag ions to preferentially form Ag NPs on ZnO nanorods. The ratio of visible emission to ultraviolet (UV) emission for the Ag NP-decorated ZnO nanorod arrays, synthesized for 30 min, is 20.5 times that for the ZnO nanorod arrays without Ag NPs. The enhancement of the visible emission is believed to associate with the surface plasmon (SP) effect of Ag NPs. The Ag NP-decorated ZnO nanorod arrays show significant SP-induced enhancement of yellow-green light emission, which could be useful in optoelectronic applications. The technique developed here requires low processing temperatures (120 °C and lower) and no high-vacuum deposition tools, suitable for applications such as flexible electronics.

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In this study, we report experimental results on the epitaxial growth of InP layer on GaAs (001) substrate by using MOCVD. We have systematically controlled nucleation steps in order to obtain InP epitaxial layers with high crystallinity quality. The controlling parameters were flow ratio of V/IIIsources and thicknesses of nucleation layer for nucleation steps. We successfully improved the surface roughness and crystallinity of IIP epitaxial layers on GaAs substrates.

Changes in structural characteristics and band alignments of atomic-layer-deposited HfO 2 films on InP (001) as a function of annealing temperature and film thickness were investigated using various analytical techniques. After an annealing at temperatures over 500 8C, the HfO 2 films were converted into a fully crystalline structure with a tetragonal phase with no detectable interfacial layer between the film and the InP substrate. In-P-O states, produced by interfacial reactions, were increased during the post deposition annealing (PDA) process and oxides were detected in the surface region of the HfO 2 film, indicating that In and P atoms had out-diffused. The E g value of the as-grown HfO 2 film was found to be 5.80 AE 0.1 eV. After the PDA treatment, the optical band gap and valence band offset values were significantly affected by the interfacial oxide states between the HfO 2 film and InP substrate. Moreover, band bending in InP, due to negative space charges generated by an unstable P-rich interfacial state during atomic layer deposition process was decreased after the annealing treatment.