Passivation of a Metal Contact with a Tunneling Layer

AbstractThe potential of contact passivation for increasing cell performance is indicated by several results reported in the literature. However, scant characterization of the tunneling layers used for that purpose has been reported. In this paper, contact passivation is investigated by insertion of an ultra-thin AlOx layer between an n-type emitter and a Ti/Pd/Ag contact. By using a 1.5nm thick layer, an increase of the minority carrier lifetime by a factor of 2.7 is achieved. Since current-voltage measurements indicate that an ohmic behavior is conserved for AlOx layers as thick as 1.5nm, a 1.5nm AlOx layer is found to be a candidate of choice for contact passivation

Charge transport after hard breakdown in gate oxides

We show measurement results and simulations of current�voltage characteristics of Metal-Oxide-Semiconductor capacitors after hard breakdown. The devices exhibit either point contact or diode behaviour, depending on electrode and substrate characteristics and the bias regime. The charge transport characteristics were reproduced in device simulations, including the dependence on the gate dimensions and breakdown spot size

Influence of gasification on the performance of a 1 MHz nozzle system in megasonic cleaning\ud

Single-wafer cleaning based on megasonic nozzle systems can be used for removing nano-particles. An optimized cleaning process must deliver a high degree of cleaning uniformity with a minimal amount of structural damage. However, the cleaning liquid is confined to a sonicated liquid jet, which is ejected by the nozzle. As a result, a high degree of complexity is introduced to the cleaning process due to the strong interdependencies between acoustic, electric and hydrodynamic characteristics of such systems. In the present work, the influence of the gas content of the cleaning liquid on the performance of a 1 MHz nozzle system is investigated and related to the intrinsic properties of the water jet. Cleaning tests are performed and the cleaning results are correlated to the electrical responses of the driving transducer. The electrical response depends both on the gasification of the liquid and the occurrence of acoustic reflections. Furthermore, Schlieren- and Sonoluminescence-imaging of the cleaning system are performed. The imaging techniques can identify the impact of bubbles on the propagation of acoustic waves and the resonant excitation of cleaning cavitation throughout the liquid column.\ud \u

Integrating surface nanotextures into thin crystalline-Si solar cells: The case of a 1-μm-thin nanoimprinted heterojunction cell

Texturing of crystalline silicon at the light wavelength scale is a promising approach for light management in ever thinner cells. However, this approach requires adapting the device design and process, which has so far revealed to be a challenging task. Indeed, successful integration requires compromising the excellent optical properties for preserving the electrical ones. We briefly summarize what has been learned so far in the community and illustrate some of these learnings with the fabrication and improvement of 1-μm-thin monocrystalline nanotextured silicon solar cells

Wet chemical treatment of boron doped emitters on n-type (100) c-Si prior to amorphous silicon passivation

10.1016/j.apsusc.2014.11.180APPLIED SURFACE SCIENCE328140-14

Passivating electron-selective contacts for silicon solar cells based on an a-Si:H/TiO\u3csub\u3ex\u3c/sub\u3e stack and a low work function metal

\u3cp\u3eIn this work, the ATOM (intrinsic a-Si:H/TiO\u3csub\u3ex\u3c/sub\u3e/low work function metal) structure is investigated to realize high-performance passivating electron-selective contacts for crystalline silicon solar cells. The absence of a highly doped Si region in this contact structure is meant to reduce the optoelectrical losses. We show that a low contact resistivity (ρ\u3csub\u3ec\u3c/sub\u3e) can be obtained by the combined effect of a low work function metal, such as calcium (Φ 2.9 eV), and Fermi-level depinning in the metal-insulator-semiconductor contact structure (where in our case TiO\u3csub\u3ex\u3c/sub\u3e acts as the insulator on the intrinsic a-Si:H passivating layer). TiO\u3csub\u3ex\u3c/sub\u3e grown by ALD is effective to achieve not only a low ρ\u3csub\u3ec\u3c/sub\u3e but also good passivation properties. As an electron contact in silicon heterojunction solar cells, inserting interfacial TiO\u3csub\u3ex\u3c/sub\u3e at the i-a-Si:H/Ca interface significantly enhances the solar cell conversion efficiency. Consequently, the champion solar cell with the ATOM contact achieves a V\u3csub\u3eOC\u3c/sub\u3e of 711 mV, FF of 72.9%, J\u3csub\u3eSC\u3c/sub\u3e of 35.1 mA/cm\u3csup\u3e2\u3c/sup\u3e, and an efficiency of 18.2%. The achievement of a high V\u3csub\u3eOC\u3c/sub\u3e and reasonable FF without the need for a highly doped Si layer serves as a valuable proof of concept for future developments on passivating electron-selective contacts using this structure.\u3c/p\u3