Limitations of the ABC Model of Recombination Rates to Describe the Internal Quantum Efficiency of Quantum Well LEDs: A Critical Analysis

An analysis of the applicability of the ABC recombination model to describing the current dependence of the internal quantum efficiency (IQE) demonstrates its inadequacy. The main criticisms are as follows: – The use of a secondary parameter for quantum-well device structures, namely the excess carrier concentration, as the argument in the current dependence of IQE, especially under the assumption of equal electron and hole concentrations in the space-charge region; – Auger recombination and radiative recombination are partial components of a unified inter-band recombination process and therefore cannot be treated as independent processes; – The ABC model unjustifiably ignores the fundamental mechanism of tunneling current formation; – In the ABC model, the origin of the nonradiative current is attributed to the Shockley – Read – Hall recombination mechanism, whereas in the device structure it is governed by the Sah – Noyce – Shockley mechanism. Based on this critical analysis, it is concluded that an adequate model describing the IQE – current dependence should be developed on the basis of the physical mechanisms governing the fundamental currents in quantum-well device structures: – The recombination current via defect levels in quantum wells, Jt; – The inter-band recombination current, JB; – The tunnelling current, JT. Such a model should also account for the unified mechanism responsible for the formation of the radiative component of inter-band recombination, (1‑p)・JB, and the nonradiative component, p・Jb, where p is the partition coefficient dependent on JB. A general expression for the current dependence of IQE is proposed as follows: ηIQE=(1‑p)・ JB /(Jt+JB+JT).