We have found with deep-level transient spectroscopy that chemical etching introduced three electron traps, E1(0.11), E2(0.13), and E3(0.15), in the near-surface region of phosphorus-doped crystalline silicon. The results on depth profiles of these traps and carriers suggested the donor character of the traps, but they hardly exhibited the Poole–Frenkel effect. From their correlations with carbon and oxygen, we propose a tentative identification that E1 and E2 traps arise from two kinds of hydrogen-oxygen-carbon complexes and the E3 trap arises from a hydrogen-carbon complex. Hydrogen is assumed to be adsorbed on the silicon surface during chemical etching and diffuse into the interior of the crystal during the subsequent evaporation and sample storage processes to be trapped at two kinds of oxygen-carbon complexes and substitutional carbon to form the traps. The annealing behavior of E2 and E3 traps in the dark were studied in detail. Their densities were increased at temperatures of 70–90 °C and subsequently were decreased at higher temperatures obeying first-order kinetics. The increase in trap densities is interpreted to be due to the further formation of the traps by capturing mobile hydrogen by oxygen-carbon complexes and substitutional carbon. This hydrogen is assumed to be released at temperatures of 70–90 °C by the dissociation of the hydrogen-phosphorus complex that was also formed by in-diffusing hydrogen during the evaporation and sample storage processes. The subsequent decrease in trap densities is attributed to the thermal dissociation of the traps at higher annealing temperatures and the subsequent loss of hydrogen at sinks. The illumination of band-gap light above 230 K annihilated the traps. The annihilation of the traps occurred only outside the depletion region of the Schottky structure. This effect is ascribed to the recombination-enhanced reaction, in which the electronic energy released by the electron-hole recombination at a trap level is converted into local vibrational energy to induce the thermal dissociation of the traps.

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N-type ZnO thin films were successfully grown by sol-gel dipping coat method on glass substrates at 300 -600 °C under air atmosphere. Poly ZnO thin films were obtained at more than 300 °C. Values of full width at half maximum of (0002) peak at the XRD spectra became small with the increasing the substrate temperatures. Optical transmittances of the ZnO thin films increased with the increasing the substrate temperatures. The optical transmittance of Ga-doped ZnO thin films was larger than In-and Al-doped ZnO films (5 wt%). Moreover, a resistivity of Ga-doped ZnO was smaller than those of In-and Al-doped ZnO films. X-ray photoemission spectroscopy (XPS) results indicated that a chemical shift of oxygen (1s) in Ga-doped ZnO was smaller than those of In-and Al-doped ZnO films. These indicated that Ga atoms were easy to substitute of Zn atoms in comparison with In and Al atoms. This result was clear from the ionic radius and the covalent radius of Ga atoms, which were similar to those of Zn compared with Al and In atoms.Introduction Wide bandgap oxide-semiconductors have attracted much attention for liquid crystal displays and solar cells. A ZnO material is a semiconductor with a hexagonal structure and a large bandgap of 3.4 eV at room temperature. Recently, ZnO based materials are much respected for UV lightemitting devices. Optically pumped UV emission at RT has been already reported [1]. Group-III elements such as Al, Ga and In, and group-VII elements such as Cl, Br and I can be used as n-type dopants in the ZnO material [2 -4].In this work, n-type ZnO thin films were grown by sol-gel dipping coat method on glass substrates at 100 -600 °C under air atmosphere. The sol-gel technique is known to have the distinct advantages of process simplicity, low cost and easiness of composition control. Precursor solutions of n-type ZnO are prepared by dissolving both 95 wt% zinc acetate dihydrate and 5 wt% Al, In or Ga acetate dihydrate into anhydrous ethanol for the solutions to have the desired group-III/Zn wt%.Crystal structures of the ZnO thin films were examined by the X-ray diffraction (XRD) measurement. Optical and electrical properties of the ZnO films were also obtained by the optical transmittance and the four-probe point measurements, respectively. X-ray photoemission spectroscopy (XPS) was used to analyze the film composition and the chemical bonding of the elements.

We have evaluated hydrogen and deuterium diffusivities in silicon below room temperature (220–270 K) by analyzing the kinetics of photoinduced dissociation of a chemical etching introduced hydrogen (deuterium)–carbon complex. Under sufficiently strong illumination, the annihilation rate of the complex was proportional to the phosphorus density, indicating that the rate-determining step is the diffusion of hydrogen (deuterium) to phosphorus atoms. Applying the diffusion-controlled reaction theory, we have evaluated the diffusion coefficients as 7×10−2exp(−0.54 eV/kT) cm2 s−1 for hydrogen and 5×10−3exp(−0.49 eV/kT) cm2 s−1 for deuterium, being in good agreement with the extrapolation of the high-temperature diffusion data of A. Van Wieringen and N. Warmoltz [Physica 22, 849 (1956)].