Back in 2002, Toshiba released its pioneer Quantum LED design.  It opened a route for electrically driven quantum light sources adapted to different spectral ranges and environments. However, several constraints of the design, like the lack of a built-in wavelength tuning mechanism, or how to surpass the large sheet resistance in nanophotonic structures, remained unsolved. Just recently, completely new approaches appeared adding new functionalities to the original design. [2,4]
We will present our own design. It is based on a vertical multijunction heterostructure where quantum light emission and tuning into photonic crystal cavities might become possible, for the first time, without constraints.  The device comprises of two separated electrical injection and electrical tuning regions in a bi-polar transistor configuration. The connection between them is purely optical and thus, it naturally avoids the sheet resistance problems that plague other approximations, especially when applied to nanophotonic devices. The first fabricated devices show single photon emission with g2(0)<0.1 at injection currents as low as 100 mA/cm2 and fully linear conversion between electrical power and single photon flux.
Z.Yuan et al Electrically Driven Single-Photon Source. Science 2002, 295, 102.
B. Alén et al “Tunable monolithic quantum light source and quantum circuit thereof” Patent pending EP/17382061.4, PCT/EP2018/052960. Date: Feb 8th 2017
J. P.Murray et al “Electrically Driven and Electrically Tunable Quantum Light Sources”. Appl. Phys. Lett. 2017, 110 (7), 071102.
P.Munnelly et al “Electrically Tunable Single-Photon Source Triggered by a Monolithically Integrated Quantum Dot Microlaser”. ACS Photonics 2017, 4 (4), 790–794.