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    Enhanced Rectification of Lanthanum Hydroxide-Doped Graphene Quantum Dots/Silicon Heterostructures at Cryogenic Temperatures
    (Wiley, 2025) Altan, Aslihan Anter; Berktas, Zeynep; Kaymak, Nuriye; Yildiz, Mustafa; Di Bartolomeo, Antonio; Orhan, Elif
    This study reports the fabrication and temperature-dependent electrical characterization of a heterojunction formed by lanthanum(III) hydroxide nanoparticles doped with polyethyleneimine-functionalised nitrogen-doped graphene quantum dots (La(OH)3NPs/PEI N-GQDs) on n-type silicon (n-type Si). The heterostructure exhibits diode-like behaviour in the 77-400 K temperature range, with rectification exceeding two orders of magnitude and increasing as the temperature decreases, reaching an exceptionally high value above 10(5) at 77 K. Temperature-dependent diode parameters, including barrier height, series resistance, and ideality factor, are extracted using the thermionic emission model, revealing that barrier height increases and ideality factor decreases with rising temperature. These trends, along with significant deviations from the ideal Richardson behaviour of Schottky diodes, are effectively explained by the Werner-G & uuml;ttler model, which attributes them to Gaussian spatial inhomogeneities of the barrier arising from interface states and nanocomposite-induced fluctuations. This study highlights the robust rectifying behaviour, excellent cryogenic performance, and wide-temperature applicability of the La(OH)3NPs/PEI N-GQDs on the Si heterostructure, establishing it as a promising platform for low-power diode applications under extreme thermal conditions.
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    Öğe
    PEI N-doped graphene quantum dots/p-type silicon Schottky diode
    (Elsevier, 2022) Berktas, Zeynep; Yıldız, Mustafa; Seven, Elanur; Orhan, Elif Oz; Altindal, Semsettin
    Graphene Quantum Dots (GQDs) are graphene nanoparticles with exceptional properties and a remarkable material for new technologies. Especially, GQDs/semiconductor junctions (GQDs/S), which have a high potential to open doors to new fields of study such as sensing, detection, and communication have started to attract great attention in the scientific community in the last few years. Functionalization of GQDs with several functional groups to develop their properties is one of the hot topics of research. In this context, we have investigated the properties of functionalized GQDs/p-type Si diode in this study. Polyethylenimine (PEI) functionalized nitrogendoped GQDs (PEI/N/GQDs) have been successfully produced by the hydrothermal method. Afterward, we fabricated the Al/PEI/N/GQDs/p-Si diode. The parameters of GQDs-based Schottky diode have been investigated from current-voltage (I-V) measurements at 300 K. The barrier heights (Phi(b)) of the diode obtained from Thermionic Emission (TE) theory, Norde's, and Cheung's approaches are 0.76 eV, 0.82 eV, and 0.66 eV, respectively. The ratio of rectification (RR) of the diode has been calculated to be approximately 2.8 x 10(4) at +/- 5 V. In addition, the surface state density (N-ss) versus (E-ss-Ev) profile of the diode has been also obtained, by taking into account the voltage dependence of the ideality factor (n) and Phi(b). The average value of them has been found as 1.90 x 10(13) eV(- 1) cm(-2), which is very suitable for this structure. The obtained results show that the prepared Al/PEI/N/GQDs/p-Si has Schottky diode behavior.