Auger recombination
Auger recombination is a three-particle non-radiative process in which the energy released by the recombination of an electron–hole pair is not emitted as light or phonons, but is instead transferred to a third carrier (another electron or hole). This additional carrier is excited to a higher energy state within its band and subsequently relaxes by dissipating energy as heat. Auger recombination therefore represents a parasitic loss mechanism, particularly important at high carrier densities.
The rate of Auger recombination is expressed as
\[R^{AU} = \big(C^{AU}_{n} n + C^{AU}_{p} p\big)\,(np - n_{0}p_{0}) \]
where \(n\) and \(p\) are the electron and hole densities, \(n_{0}\) and \(p_{0}\) are their equilibrium values, and \(C^{AU}_{n}\) and \(C^{AU}_{p}\) are the electron- and hole-assisted Auger coefficients with units of m6s−1. These coefficients set the probability that the recombination energy of an electron–hole pair is transferred to a free electron (\(C^{AU}_{n}\)) or to a free hole (\(C^{AU}_{p}\)).
The key feature of Auger recombination is its strong carrier-density dependence: the rate scales with the square of the carrier density (through the \(np\) term) and is further weighted by either \(n\) or \(p\) through the prefactor. This makes Auger recombination negligible at low injection but dominant under high-level injection or in heavily doped semiconductors.
In practice, Auger recombination is a critical loss channel in III–V semiconductors (e.g. GaAs, InGaN), silicon solar cells under strong illumination, high-brightness LEDs, and semiconductor lasers, where very high carrier densities are routinely present. It has also been identified as a limiting factor in some inorganic perovskites under concentrated sunlight or pulsed-laser excitation. By contrast, in organic semiconductors and typical thin-film devices operating under 1-sun solar cell conditions, carrier densities are too low for Auger recombination to play a significant role, and trap-assisted or bimolecular pathways dominate instead.
In OghmaNano, the values of \(C^{AU}_{n}\) and \(C^{AU}_{p}\) can be set directly in the Electrical parameter editor. This allows Auger recombination to be included when modelling devices where high carrier densities are expected to influence efficiency and performance losses.