Degenerate two-photon absorption (TPA) is investigated in a 186 nm thick gallium arsenide (GaAs) p-i-n diode embedded in a resonant metallic nanostructure. The full device consists in the GaAs layer, a gold subwavelength grating on the illuminated side, and a gold mirror on the opposite side. For TM-polarized light, the structure exhibits a resonance close to 1.47 μm, with a confined electric field in the intrinsic region, far from the metallic interfaces. A 109 times increase in photocurrent compared to a non-resonant device is obtained experimentally, while numerical simulations suggest that both gain in TPA-photocurrent and angular dependence can be further improved. For optimized grating parameters, a maximum gain of 241 is demonstrated numerically and over incidence angle range of (−30°; +30°).
The luminescence properties of Nd-doped SiOx layers containing silicon nanocrystals (Si-ncs) were investigated by steady state, time-dependent and power-dependent photoluminescence spectrometry and photoluminescence excitation experiments. Both direct and indirect excitation processes of Nd3+ ions have been evidenced. The energy transfer mechanism between Si-ncs and Nd3+ ions is favored by the overlap between the emission spectrum of confined excitons in Si-ncs and the Nd3+ absorption from the ground state to 4F5/2 electronic level. The more intense Nd-related emission was obtained in samples containing 0.5 at. % of Nd and characterized by an indirect excitation cross section equal to 8 × 10−15 cm2.
Planar conjugated molecular backbones are essential for achieving high charge carrier mobilities along molecular -stacking directions but are often concomitant with poor charge transport in other directions. This is particularly...
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