B. G. Svensson

Identification of oxygen and zinc vacancy optical signals in ZnO

Photoluminescence spectroscopy has been used to study single crystalline ZnO samples systematically annealed in inert, Zn-rich and O-rich atmospheres. A striking correlation is observed between the choice of annealing ambient and the position of the deep band emission (DBE) often detected in ZnO. In particular, annealing in O2 results in a DBE at 2.35±0.05eV, whereas annealing in the presence of metallic Zn results in DBE at 2.53±0.05eV. The authors attribute the former band to zinc vacancy (VZn) related defects and the latter to oxygen vacancy (VO) related defects. Additional confirmation for the VO and VZn peak identification comes from the observation that the effect is reversible when O- and Zn-rich annealing conditions are switched. After annealing in the presence of ZnO powder, there is no indication for the VZn- or VO-related bands, but the authors observe a low intensity yellow luminescence band peaking at 2.17eV, probably related to Li, a common impurity in hydrothermally grown ZnO.

Electronic structure and optical properties of ZnX (X=O, S, Se, Te): A density functional study

Electronic band structure and optical properties of zinc monochalcogenides with zinc-blende- and wurtzite-type structures were studied using the ab initio density functional method within the local-density approximation (LDA), generalized-gradient approximation, and

Gettering of transition metal impurities during phosphorus emitter diffusion in multicrystalline silicon solar cell processing

\mathrm{LDA}+U

Generation of divacancies in silicon irradiated by 2‐MeV electrons: Depth and dose dependence

approaches. Calculations of the optical spectra have been performed for the energy range

Annealing behavior between room temperature and 2000 °C of deep level defects in electron-irradiated n-type 4H silicon carbide

0\char21{}20\phantom{\rule{0.3em}{0ex}}\mathrm{eV}

Palladium Schottky barrier contacts to hydrothermally grown n-ZnOand shallow electron states

, with and without including spin-orbit coupling. Reflectivity, absorption and extinction coefficients, and refractive index have been computed from the imaginary part of the dielectric function using the Kramers-Kronig transformations. A rigid shift of the calculated optical spectra is found to provide a good first approximation to reproduce experimental observations for almost all the zinc monochalcogenide phases considered. By inspection of the calculated and experimentally determined band-gap values for the zinc monochalcogenide series, the band gap of ZnO with zinc-blende structure has been estimated.

Zinc oxide: bulk growth, role of hydrogen and Schottky diodes

We have investigated the gettering of transition metals in multicrystalline silicon wafers during a phosphorus emitter diffusion for solar cell processing. The results show that mainly regions of high initial recombination lifetime exhibit a significant lifetime enhancement upon phosphorus diffusion gettering. Nevertheless, transition metal profiles extracted by secondary ion mass spectrometry in a region of low initial lifetime reveal significant gradients in Cr, Fe, and Cu concentrations towards the surface after the emitter diffusion, without exhibiting a significant enhancement in the lifetime. In a region of higher initial lifetime, however, diminutive concentration gradients of the transition metal impurities are revealed, indicating a significantly lower initial concentration in these regions. From spatial maps of the dislocation density in the wafers, we find that lifetime enhancements mainly occur in regions of low dislocation density. Thus, it is believed that a generally higher concentration of...

High concentration in-diffusion of phosphorus in Si from a spray-on source

Czochralski‐grown silicon samples (n‐type) have been irradiated by 2‐MeV electrons at room temperature to doses in the range of 1015–1016 cm−2. The generation of divacancies (V2) has been studied as a function of bombardment dose and sample depth using deep‐level transient spectroscopy (DLTS). In the DLTS spectra, a level ∼0.41 eV below the conduction band is attributed to V2 in accordance with previous assignments made by other authors. It is shown that the generation rate of V2 is not only determined by the primary electron energy, but also depends on the bombardment dose. Initially, the divacancy concentration depends linearly on dose while at high doses a gradual decrease in the generation rate occurs. The concentration of V2 increases significantly with depth close to the surface (≤3 μm) while for larger depths a constant value is reached. The experimental depth profiles are qualitatively compared with a theoretical curve. This curve is calculated assuming vacancy diffusion, and it is speculated that...

Coulomb correlation effects in zinc monochalcogenides

The annealing behavior of irradiation-induced defects in 4H-SiC epitaxial layers grown by chemical-vapor deposition has been systematically studied by means of deep level transient spectroscopy (DL ...

Electrical characteristics of palladium Schottky contacts to hydrogen peroxide treated hydrothermally grown ZnO

Schottky barrier contacts have been formed by electron beam evaporation of Pd on the (0001¯)-face of hydrothermally grown n-type single-crystalline ZnO. The contacts can be operated under reverse bias voltages up to −5V and in the temperature range between 130 and 350K. A barrier height of 0.83eV is deducted at room temperature, which is in reasonable agreement with the value predicted by fundamental theory. The ideality factor for the current-voltage characteristics varies between 1.01 and 1.03 in the voltage range of −5.0to+0.5V, indicating that thermionic emission is a dominant mechanism for charge-carrier transport. Thermal admittance measurements were performed between 15 and 350K, and two prominent levels were resolved at 0.05(1) and 0.33(2)eV below the conduction band edge, respectively. The origin of these levels is not known, but possible candidates are complexes involving hydrogen, Zn interstitials, and vacancy-oxygen centers.