The effect of etchants on surface of CdTe single crystal

Cadmium telluride crystals (CdTe) have been grown by the sublimation method. The crystal polarity of the CdTe with the zincblend structure has been studied. Two different crystallographic defect and etch pits are revealed on the (111) Cd and  Te surfaces by different etchant.

Simulation of Dislocation Accumulation in Impurity Doped-ULSI Cells and Electric Characteristic Evaluations

The performance of semiconductor devices has improved on introducing increasing refinements to the structures of these devices. This has created various problems at the atomic level. In particular, the presence of dislocations, a type of crystallographic defect, within semiconductor devices poses a major problem. Dislocations accumulated within the device obstruct the movement of electrons and adversely affect the electrical characteristics of the device. However, previous investigations have not sufficiently clarified the relationship between accumulated dislocations and the electrical characteristics of a semiconductor. In this study, we focus on dislocations produced in the fabrication of an impurity-doped ultra-large-scale integration (ULSI) device and, based on a crystal plasticity analysis, perform a simulation of the accumulation of dislocations within the device during the cooling process. We establish an analytical system by which the obtained information on dislocations is applied to a device simulator, in order to evaluate the electrical characteristics by considering the accumulation of dislocations. We investigate the effects that dislocation density and density distribution have on the characteristic current-voltage curve of the device.

Evidence and Characterization of Crystallographic Defect and Material Quality after SLIM-Cut Process

ABSTRACTThe SLIM-Cut process is a kerf-free wafering technique to obtain silicon substrates as thin as 50μm. The quality of the resulting material must be assessed to ensure that this innovative Si-foil approach does not jeopardize the potential efficiency of the final solar cell in terms of electronic activity, defect density and location. For that reason, we performed Microwave-Detected Photoconductance Decay (MW-PCD), Deep-Level Transient Spectroscopy (DLTS) and optical inspections after defect etching of the foils surface. Analyses indicate that SLIM-Cut generates crystallographic defects which create deep level traps that have a negative impact on the lifetime of the silicon foil. Nonetheless, a decrease of the thermal budget will lead to a reduction of plasticity and hence lower the amount of defects and increase the foil quality.

Carrier Transport in Homo- and Heteroepitaxial Zinc Oxide Layers

Homo- and heteroepitaxial ZnMgO:Al, ZnCaO:Al and ZnO:Ga films have been grown on sapphire and ZnO substrates by RF (13.56 MHz) reactive magnetron sputtering from oxidic targets. The films grow epitaxially, i.e. with a preferred in-plane and out-of plane orientation. However, the heteroepitaxial films on sapphire exhibit a much higher crystallographic defect density, compared to the homepitaxial films. The ZnMeO films (Me – metal)on a-plane sapphire exhibit a lower defect density leading to higher Hall mobilities. Both, homo- and heteroepitaxial ZnO:Ga films with carrier concentrations N>1020 cm−3 exhibit the same mobility values, which increase with increasing carrier concentration. This behaviour is typical for electrical grain barrier limited transport, as decribed recently for polycrystalline ZnO:Al(Ga) films on glass. For the ZnCaO:Al films, deposited at similar conditions as the ZnO:Ga films, much lower carrier concentrations were measured, both for sapphire as well as for ZnO substrates. The mobilities of the ZnCaO:Al films on ZnO are much higher than that on the sapphire single crystals. The measured Hall mobilities are compared to single crystalline ZnO transport data.Additionally, the work functions of the ZnMeO layers have been measured by X-ray and ultra-violet photoelectron spectroscopy. As expected, the work functions are lower compared to unalloyed ZnO, which can be used for ZnO band gap and band alignment engineering.

Physics and Electrochemistry of Oxide Growth

The growth of the passive film on tungsten in phosphate buffer solution has been described in terms of the Point Defect Model (PDM). The steady-state current and passive film thickness have been measured as a function of voltage, with the film thickness being obtained from an analysis of capacitance and reflectance data. The observed data cannot be accounted for by the High Field Model (HFM) in its classical form, but can be understood in terms of the PDM. Diagnostic criteria that have been derived from the PDM were used to identify the majority charge carriers in the passive film. The Point Defect Model was employed, together with Mott- Schottky analysis to explore the crystallographic defect structures of the passive films, whereas their electronic structures have been studied using photoelectrochemical impedance spectroscopy (PEIS). The experimental results demonstrate that these structures are strongly coupled with the vacancies acting as the dopants.