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.

Lasers & gainOptics fundamentals

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).