New architectures of transparent conductive electrodes (TCEs) incorporating graphene monolayers in different configurations have been explored with the aim to improve the performance of silicon-heterojunction (SHJ) cell front transparent contacts. In SHJ technology, front electrodes play an important additional role as anti-reflectance (AR) coatings. In this work, different transparent-conductive-oxide (TCO) thin films have been combined with graphene monolayers in different configurations, yielding advanced transparent electrodes specifically designed to minimize surface reflection over a wide range of wavelengths and angles of incidence and to improve electrical performance. A preliminary analysis reveals a strong dependence of the optoelectronic properties of the TCEs on (i) the order in which the different thin films are deposited or the graphene is transferred and (ii) the specific TCO material used. The results shows a clear electrical improvement when three graphene monolayers are placed on top on 80-nm-thick ITO thin film. This optimum TCE presents sheet resistances as low as 55 Ω/sq and an average conductance as high as 13.12 mS. In addition, the spectral reflectance of this TCE also shows an important reduction in its weighted reflectance value of 2–3%. Hence, the work undergone so far clearly suggests the possibility to noticeably improve transparent electrodes with this approach and therefore to further enhance silicon-heterojunction cell performance. These results achieved so far clearly open the possibility to noticeably improve TCEs and therefore to further enhance SHJ contact-technology performance.
Gd-rich gadolinium scandate (Gd 2-x Sc x O 3) was deposited by high-pressure sputtering on (1 0 0) silicon by alternating the deposition of <0.5 nm thick films of its binary components: Sc 2 O 3 and Gd 2 O 3. The formation of the ternary oxide was observed after the thermal treatments, with a high increase in the effective permittivity of the dielectric (up to 21). The silicon diffuses into the Gd 2-x Sc x O 3 films, which show an amorphous character. After the annealing no interfacial silicon oxide is present. C HF-V G curves indicated low hysteresis (55 mV) and a density of interfacial defects of 6 × 10 11 eV-1 cm-2 .
Articles you may be interested inOptimization of in situ plasma oxidation of metallic gadolinium thin films deposited by high pressure sputtering on silicon J.Embedded argon as a tool for sampling local structure in thin plasma deposited aluminum oxide films Structural, optical, and electrical characterization of gadolinium oxide films deposited by low-pressure metalorganic chemical vapor deposition High j gadolinium oxide thin layers were deposited on silicon by high-pressure sputtering (HPS). In order to optimize the properties for microelectronics applications, different deposition conditions were used. Ti (scavenger) and Pt (nonreactive) were e-beam evaporated to fabricate metal-insulator-semiconductor (MIS) devices. According to x-ray diffraction, x-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy, polycrystalline stoichiometric Gd 2 O 3 films were obtained by HPS. The growth rate decreases when increasing the deposition pressure. For relatively thick films (40 nm), a SiO x interface as well as the formation of a silicate layer (GdSiO x ) is observed. For thinner films, in Ti gated devices the SiO x interface disappears but the silicate layer extends over the whole thickness of the gadolinium oxide film. These MIS devices present lower equivalent oxide thicknesses than Pt gated devices due to interface scavenging. The density of interfacial defects D it is found to decrease with deposition pressure, showing a reduced plasma damage of the substrate surface for higher pressures. MIS with the dielectric deposited at higher pressures also present lower flatband voltage shifts DV FB in the C HF -V G hysteresis curves.
AlGaN/GaN HEMTs and MOS-HEMTs using Gd2O3 as gate dielectric were irradiated with 2 MeV protons up to fluence of 1 × 10 15 cm -2 . Results showed that proton irradiation causes a strong degradation in the Schottky gate devices, featured by more than three orders of magnitude increase in reverse leakage current, a 30% decrease in maximum drain current and same percentage of increase in ON-resistance, respectively. Scanning transmission electron microscopy showed that radiation induced a diffusion of Ni into Au in the gate and void formation, degrading the transistors characteristics. The Gd2O3 gate dielectric layer prevented this diffusion and void formation. MOS-HEMTs with Gd2O3 gate dielectric show 50% less decrease of performance under proton irradiation than Schottky gate HEMTs (conventional HEMTs). The trapping effects of Gd2O3 gate layer before and after irradiation are also discussed.
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