A Unipolar Quantum Dot Diode Structure for Advanced Quantum Light Sources

Triggered, indistinguishable single photons are crucial in various quantum photonic implementations. Here, we realize a novel n(+)-i-n(++) diode structure embedding semiconductor quantum dots: the gated device enables spectral tuning of the transitions and deterministic control of the charged states. Blinking-free single-photon emission and high two-photon indistinguishability are observed. The line width's temporal evolution is investigated across over 6 orders of magnitude time scales, combining photon-correlation Fourier spectroscopy, high-resolution photoluminescence spectroscopy, and two-photon interference (visibility of V-TPI,V-2ns = (85.8 +/- 2.2)% and V-TPI,V-9ns = (78.3 +/- 3.0)%). Most of the dots show no spectral broadening beyond similar to 9 ns time scales, and the photons' line width ((420 +/- 30) MHz) deviates from the Fourier-transform limit by a factor of 1.68. The combined techniques verify that most dephasing mechanisms occur at time scales <= 2 ns, despite their modest impact. The presence of n-doping implies higher carrier mobility, enhancing the device's appeal for high-speed tunable, high-performance quantum light sources.