We report on the device characteristics of amorphous indium gallium zinc oxide thin-film transistors (TFTs) with aluminum (Al) electrodes. The TFTs exhibited a high performance with a field-effect mobility of 11.39 cm2/V s, a subthreshold swing of 181 mV/ decade, and an on-off ratio of 107. Further improvement in device performance was achieved by doping the source/drain contact regions, resulting in an enhanced mobility of 16.6 cm2/V s at an operating voltage as low as 5 V.
Complementary inverters composed of pentacene for the p-channel thin-film transistors (TFTs) and amorphous indium gallium zinc oxide for the n-channel TFTs have been fabricated on glass substrates. The p- and n-channel TFTs have field-effect mobilities of 0.6 and 17.1 cm2/V s, respectively, and inverters yield a high gain of ∼56. Complementary five-stage ring oscillator exhibits a good dynamic operation with an output frequency of 200 Hz at 10 V. Since both channel layers are stable in air and can be formed by room temperature deposition process, the hybrid circuits are applicable to flexible electronic devices.
Carrier localization in InGaN∕GaN multiple-quantum wells (MQWs) with three different well thicknesses was investigated optically using time-integrated and time-resolved microphotoluminescence spectroscopy. An anomalous temperature dependence of the photoluminescence peak energy was observed, as a consequence of local potential fluctuations. The carrier localization was more prominent in the case of MQWs with wide well thickness. The results indicate that the degree of potential fluctuation increases with increasing well thickness. Emission from quantum-dot-like states only became apparent in MQWs with wide well thickness, which supports the assertion that carrier localization in InGaN∕GaN MQWs is due to the formation of quantum dots.
We fabricated light-emitting hybrid p-n junction devices using low temperature deposited ZnO and organic films, in which the ZnO and the organic films served as the n- and p-type component, respectively. The devices have a rectification factor as high as ∼103 and a current density greater than 2 A/cm2. Electroluminescence of the hybrid device shows the mixture of the emission bands arising from radiative charge recombination in organic and ZnO. The substantial device properties could provide various opportunities for low cost and large area multicolor light-emitting sources.
Time-resolved and time-integrated microphotoluminescence spectrometry of exciton and
biexciton transitions in a single self-assembled InGaN quantum dot gives sharp peaks, with the
biexciton 41 meV higher in energy. Theoretical modelling in the Hartree approximation (using
a self-consistent finite difference method) predicts a splitting of up to 51 meV. Time-resolved
microphotoluminescence measurements yield a radiative recombination lifetime of
1.0 ± 0.1 ns for the
exciton and 1.4 ± 0.1 ns for the biexciton. The data can be fitted to a coupled DE rate equation model,
confirming that the exciton state is refilled as biexcitons undergo radiative decay.
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