Visible-light-driven water splitting was investigated in a dye sensitized photoelectrosynthesis cell (DSPEC) based on a photoanode with a phosphonic acid-derivatized donor-π-acceptor (D-π-A) organic chromophore, 1, and the water oxidation catalyst [Ru(bda)(4-O(CH)P(OH)-pyr)], 2, (pyr = pyridine; bda = 2,2'-bipyridine-6,6'-dicarboxylate). The photoanode was prepared by using a layering strategy beginning with the organic dye anchored to an FTO|core/shell electrode, atomic layer deposition (ALD) of a thin layer (<1 nm) of TiO, and catalyst binding through phosphonate linkage to the TiO layer. Device performance was evaluated by photocurrent measurements for core/shell photoanodes, with either SnO or nanoITO core materials, in acetate-buffered, aqueous solutions at pH 4.6 or 5.7. The absolute magnitudes of photocurrent changes with the core material, TiO spacer layer thickness, or pH, observed photocurrents were 2.5-fold higher in the presence of catalyst. The results of transient absorption measurements and DFT calculations show that electron injection by the photoexcited organic dye is ultrafast promoted by electronic interactions enabled by orientation of the dye's molecular orbitals on the electrode surface. Rapid injection is followed by recombination with the oxidized dye which is 95% complete by 1.5 ns. Although chromophore decomposition limits the efficiency of the DSPEC devices toward O production, the flexibility of the strategy presented here offers a new approach to photoanode design.

N-polar InN quantum dots and thin layers grown by metal organic chemical vapor deposition were shown to exhibit tunable emission from around 1.00 μm to longer than 1.55 μm at room temperature. The emission wavelength was dependent on both the growth temperature and quantum dot size or InN layer thickness. No measurable change in InN quantum dot emission wavelength or intensity was observed after capping of the InN quantum dots with GaN, paving the way for incorporating N-polar InN quantum dots into buried regions of device structures.

Metal‐polar InN quantum dots (QDs) are grown by metalorganic chemical vapor deposition at temperatures between 500 and 600 °C. Dot densities between 4 × 108 and 4 × 1010 cm−2 are observed. InN QDs exhibit room‐temperature photoluminescence (PL) with peak wavelengths from 1100  to >1550 nm. GaN cap layers grown on InN QDs have little effect on either peak PL wavelength or intensity, a step toward creating multilayer structures for InN QD devices.

Heterogeneous integration of materials systems for devices and circuits is becoming of increasing interest, particularly for the wide bandgap nitrides in both optoelectronic and electronic applications. However, typical high growth temperatures of GaN by metalorganic vapor phase epitaxy prevent the growth of GaN on wafers with temperature sensitive materials. This work presents a flow modulation epitaxy (FME) growth scheme which allows for step-flow growth of GaN at temperatures below 600 • C. The utilization of a pulsed growth scheme such as FME allows for the mitigation of challenges associated with limited motion of adatoms at lower growth temperatures. Factors such as temperature, precursor flow rate, cycle time, and film thickness were explored. Under optimized conditions, step-flow growth of GaN films at 550 • C was demonstrated. In addition to an improved surface morphology over layers grown in the conventional continuous growth mode, the carbon and oxygen residual impurity concentrations in the FME grown layers were significantly lower, with carbon and oxygen contents of 9 × 10 17 cm −3 and 8 × 10 16 cm −3 , respectively. Although the growth rate of the low temperature growth was very slow, ~0.006 Å/s, the flow modulation growth scheme developed here provides a pathway towards further integration of GaN with temperature sensitive materials.

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