Anti-bunched photons from a lateral light-emitting diode
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(Color online) (a) Fabrication scheme of the p-n lateral junction. The light gray (yellow) rectangles represent the p-type and n-type contacts. The left (red) and right (blue) shaded areas respectively represent the n- and p-doped region induced by the annealing procedure. (b) Electroluminescence spectra collected increasing the forward bias from 1.45 V to 1.95 V in steps of 0.05 V at a temperature of 10 K. At lower injection current the emission, characterized by a double-peak structure, is originated by the recombination of neutral excitons and positively charged excitons. Increasing the injection current, a third peak at lower energy appears originating from recombination of electron trapped in carbon defects within the GaAs. At higher injection current, a fourth line appears due to recombination from the first excited sub-band. (c) X, blue dots (X+, black squares): areas of the emission peaks centered at 1.523 eV (1.518 eV) as a function of the injection current in logarithmic scale. The areas are derived by means of a best-fitting procedure with a sum of two Lorentzian. The linear fits, shown as dashed lines, yielded slope values of A X = 2.3 ± 0.3 . This is consistent with the expected faster increase of the peak area of the neutral excitons with respect to that of the positively charged exciton in a 2DHG.12
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(Color online) g(2)(0) as a function of (V dc ). The p-type contact was grounded. The value of g(2)(0) is derived from the ratio between the correlation counts K at τ = 0 and the average among the correlation counts of the peaks with τ ≠ 0. Lowering the injection current the value of g(2)(0) decreases down to 0.8 ± 0.1 demonstrating anti-bunched emission. Insets: Spatially resolved electroluminescence measurements of the junction region in the spot-emission and in the high-injection regimes at a temperature of 4 K. The scale of the light intensity is in arbitrary units. Emission maps were recorded by focusing emitted light on a CCD camera, through a 10 × microscope objective. The resolution of this setup is much lower than that obtained with the 0.68-NA aperture lens. Temperature was 4 K. The edges of the n-contact [dashed (red) line] and of the 2DHG [dotted (blue) line] are also reported. (a) Spot-emission regime. The device was forward biased with Vdc = −0.96 V plus voltage pulses with width and periodicity of 5 ns and 100 ns, respectively. The scale of the light intensity is in arbitrary units. (b) High-injection regime. The device was forward biased with Vdc = −3 V.
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(Color online) (a) Correlation counts (K) as a function of the delay time (τ). The LLED was biased with pulses of 3 ns of width, with a repetition period of 80 ns and V dc = −0.86 V. The pulse amplitude was reduced by an 8-dB attenuator lowering the amplitude-jitter. After a collection time of 12 h, we measured about 80 correlation counts at each peak. The measurement shows equally spaced peaks, indicated by the arrows and labeled with the peak index PI. A suppressed 0-time delay peak proves the anti-bunched emission, as confirmed by the calculated value of g (2)(0) = 0.7 ± 0.1. (b) Width of the peaks as a function of the peak index when the LLED emits Poissonian light (g (2)(0) = 1.0 ± 0.1, red squares) and in antibunching regime (g (2)(0) = 0.7 ± 0.1, blue dots).
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