Effect of the silicon doping level and features of nanostructural arrangement on decrease in external quantum efficiency in InGaN/GaN light-emitting diodes with increasing current

A comprehensive study of blue light-emitting diodes based on quantum-well InGaN/GaN structures with external quantum efficiencies η of up to 40% has been carried out. It is shown that, in the general case, the manner in which the efficiency depends on the current density j is determined by the competition of contributions to the radiative recombination of localized and delocalized carriers. The contribution of the latter grows with worsening structural organization of the nanomaterial, increasing temperature and drive current, and decreasing width of the depleted layer in the active region (under zero bias). The steepest efficiency droop relative to the maximum value (by up to a factor of 2 at j ≈ 50 A cm−2) is observed in the case of heavy doping of the n+-region (to 1019 cm−3) and upon appearance of compensated layers in the active or p+-region. At j > 50 A cm−2, the contribution of delocalized carriers is predominant and the current dependences of efficiency are of uniform type, approximated with η(j) ∝ j−b, where 0.2 < b < 0.3.