Institute of High Pressure Physics

The strong electric field in wide InGaN/GaN wells causes spatial separation of electrons and holes in the ground state.

Fig.1 Potential profile in the In_0.17Ga_0.83N/GaN well and energy levels of electrons (blue) and holes (red). The length of the bars shows the range of the wave function at a given level. It can be seen that the lowest states of electrons and holes do not overlap, so transitions between these states are prohibited, while the higher excited states can participate in recombination (radiative and non-radiative).

The wave functions of electrons and holes in the ground states do not overlap, but they effectively shield the electric field in the well. The charge in these states is called "dark charge" (because recombination is unlikely). We can only detect the presence of a "dark charge" by its effect on light emission from excited states. The research was performed by Artem Bercha, Grzegorz Muziol, Mikolaj Chlipala and Witold Trzeciakowski from our Institute, and the results are published in the work Long-Lived Excitations in Wide (In,Ga)N/GaN Quantum Wells, PHYSICAL REVIEW APPLIED 20, 034040 (2023), demonstrating the long the lifetime of a dark charge (on the order of milliseconds), while the lifetimes in typical quantum wells are on the order of nanoseconds.