Photonica
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Glossary entry

Auger recombination

A non-radiative carrier recombination process in which the energy of an electron–hole pair is transferred to a third carrier rather than emitted as a photon. The dominant non-radiative loss in long-wavelength III–V semiconductor lasers.

In Auger recombination, an electron and hole recombine without emitting a photon; instead, the released energy is transferred to a third carrier (electron or hole), promoting it to a higher state. The energy then thermalizes via phonon emission, ultimately becoming heat.

The Auger recombination rate scales as the third power of carrier density:

RAuger  =  C n3(intrinsic, n=p),R_\text{Auger} \;=\; C \, n^3 \quad (\text{intrinsic, } n = p),

or more generally R=Cnn2p+Cpnp2R = C_n n^2 p + C_p n p^2 for the electron-Auger and hole-Auger processes. CC is the Auger coefficient with units of cm6^6/s.

Typical Auger coefficients at 300 K:

MaterialCC (cm6^6/s)Emission λ\lambda
GaAs (bulk)∼1×10−30\sim 1 \times 10^{-30}870 nm
AlGaAs (λ≈850\lambda \approx 850 nm)1−5×10−301 - 5 \times 10^{-30}750 – 850 nm
InGaAs/GaAs QW∼5×10−30\sim 5 \times 10^{-30}980 nm
InGaAsP/InP (bulk, 1.55 μm)∼3×10−28\sim 3 \times 10^{-28}1300 – 1550 nm
InGaAlAs/InP MQW (1.55 μm)∼5×10−29\sim 5 \times 10^{-29}1550 nm
InGaAsSb (mid-IR, 2 – 3 μm)∼10−27\sim 10^{-27}2 – 3 μm

Auger recombination becomes severe as the bandgap decreases — the energy released by electron–hole recombination becomes resonant with available carrier transitions, dramatically increasing the matrix element. This is the dominant reason why:

  • InP-based lasers have lower T0T_0 (∼50\sim 50–7070 K) than GaAs-based lasers (∼120\sim 120–160160 K) — see characteristic temperature
  • Mid-IR semiconductor lasers (≥2\geq 2 μm) operate inefficiently at room temperature; quantum cascade lasers were developed in part to bypass Auger by using unipolar (electron-only) transitions
  • Threshold current density scales steeply with temperature in long-wavelength lasers

The strong temperature dependence of Auger (C(T)≈C0exp⁡(−Ea/kT)C(T) \approx C_0 \exp(-E_a/kT) in some models) is what makes InGaAsP devices particularly sensitive to active-region heating. Pulsed measurement is often required for accurate parameter extraction (see Pulsed vs Continuous-Wave LIV Measurement).