We report pulsed laser deposition being a quite suitable growth method for smooth and transparent p-type copper iodide (CuI) thin films with tailored electrical properties. The film characteristics are strongly influenced by the temperature during growth. Increasing substrate temperatures result in significant improvements in crystallinity compared to deposition at room temperature. In contrast to other growth techniques, the hole carrier density p can be varied systematically between 5 × 1016 cm−3 and 1 × 1019 cm−3 with hole mobilities up to 20 cm2/V s for lowest p. The surfaces exhibit irregularly shaped grains, and the roughness can be decreased down to 1 nm. Furthermore, the samples exhibit high transmittance up to 90% in the visible spectrum.

For every semiconducting material, the long-term stability of thin film characteristics is a crucial necessity for device applications. This is particularly true for the p-type semiconductor CuI, where the thin film properties are especially sensitive to environmental influences and motivate the application of capping materials. Utilizing pulsed laser deposition (PLD) and Al2O3 cappings, we performed systematic studies on the N2/O2 partial pressure during growth and the effect of layer thickness. Our results suggest that oxygen, acting as an acceptor, and its diffusion through Al2O3 and CuI dominate the conductivity of PLD grown CuI thin films. The diffusion process of atmospheric oxygen into CuI was traced with 18O-isotopes. Additionally, the transparency and morphology of CuI films are also affected by the oxygen supply during capping growth. These results challenge the currently accepted idea that intrinsic, and not extrinsic, effects determine the conductivity of CuI thin films.

The impact of the intentional selenium doping of CuI thin films is investigated concerning crucial crystalline, electrical and optical properties. For selenium contents in between 0.1 at.% and 1 at.%, the carrier density can be systematically adjusted by the selenium supply during growth between cm and cm while transparency and crystallinity remain unaffected. By temperature‐dependent Hall‐effect measurements, a carrier freeze out is observed and the binding energy of the selenium dopant is determined. The long‐term electrical stability in combination with cappings is significantly improved compared to undoped or oxygen doped CuI. However, for selenium contents exceeding 1 at.%, major crystalline changes are observed that are presumably correlated to a phase transformation. Transmission and electrical measurements suggest that the solubility limit of Se in CuI is about 1 at.% since a degradation of the transparency and decreasing free hole densities are observed for Se contents exceeding 1 at.%. Hence, the doping limit for Se in CuI corresponds to 1 at.%.

We report on temperature-dependent (10 K – 250 K) spectral and dynamical properties of free exciton–polariton and bound exciton emission in copper iodide (CuI) bulk single crystals analyzed by means of time-resolved photoluminescence spectroscopy. The characteristic line shape of the polariton emission at low temperatures is interpreted in terms of the “k-linear term effect” on the degenerate Z1,2 excitons in CuI. For free exciton–polaritons, an increase in the decay time with increasing temperature up to 360 ps at 160 K is observed. For bound exciton emission, decay times between 180 ps and 380 ps are observed at low temperatures, revealing the expected EB3/2 dependence of radiative lifetime on the localization energy. Based on the observed rise times of bound excitons at low temperatures, a defect density of shallow acceptors of 1 × 1017 cm−3 was estimated, in agreement with measured room temperature free hole density.

Atomic layer deposition of Al-doped ZnO thin films J. Vac. Sci. Technol. A 31, 01A109 (2013); 10.1116/1.4757764 Growth morphology and electrical/optical properties of Al-doped ZnO thin films grown by atomic layer deposition J. Vac. Sci. Technol. A 30, 021202 (2012); 10.1116/1.3687939 Effect of metal-ion doping on the optical properties of nanocrystalline ZnO thin films J. Appl. Phys. 99, 014306 (2006); 10.1063/1.2158503 Structural, electrical, and optical properties of transparent conductive oxide ZnO:Al films prepared by dc magnetron reactive sputtering

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