Evidence for trap-assisted Auger recombination in MBE grown InGaN quantum wells by electron emission spectroscopy

Abstract

We report on the direct measurement of hot electrons generated in the active region of blue light-emitting diodes grown by ammonia molecular beam epitaxy by electron emission spectroscopy. The external quantum efficiency of these devices is <1% and does not droop; thus, the efficiency losses from the intrinsic, interband, electron-electron-hole, or electron-hole-hole Auger should not be a significant source of hot carriers. The detection of hot electrons in this case suggests that an alternate hot electron generating process is occurring within these devices, likely a trap-assisted Auger recombination process.

Quantitative correlation of hot electron emission to Auger recombination in the active region of c-plane blue III-N LEDs

“…The magnitude of Γ valley is higher than that of the side valley, unlike previous reported EES spectra of commercial LEDs with much thicker p-GaN, 7,9-11 but more similar to Ref. 15 where the sample had 85 nm p-GaN. 15 This is notable as it suggests that with thinner p-GaN more Γ valley electrons can reach the sample surface to be emitted.…”

“…15 where the sample had 85 nm p-GaN. 15 This is notable as it suggests that with thinner p-GaN more Γ valley electrons can reach the sample surface to be emitted. In fact, the side valley mainly depopulates by scattering into the Γ valley since the side valley electrons have very few recombination pathways due to weaker radiative recombination or SRH recombination because of the larger energy difference and limited k-extension of defects.…”

“…This n 2 dependence of hot electrons may be attributed to trap-assisted Auger recombination (TAAR). 11,15,16 At the same time, the LED has an EBL in its structure, which is expected to mitigate both escape and overshoot of electrons from the active region. 1 Simulations also showed that leakage currents are small compared to Auger currents.…”

“…Combining this knowledge with the carrier density dependence of Γ valley electrons, it is possible that the source of detected Γ valley electrons is either by scattering of Auger electrons from the side valley, and/or by 3-body eeh or 2-body TAAR events. 11,15,16 Therefore the integrated intensity of Γ valley electrons is also a good proxy for hot carriers. Given the n 3 dependence of 3-body Auger recombination, it is expected that Auger recombination current will dominate rapidly over radiative recombination current with increasing injected carrier density.…”

Impact of carrier diffusion on the internal quantum efficiency of InGaN quantum well structures

“…To quantify IQE, very often the so-called ABC model is employed: 6,7 Here, N denotes the carrier density, while A , B , and C are recombination coefficients ascribed to Shockley–Read–Hall (SRH), band-to-band, and intrinsic Auger recombination, respectively. Eqn (1) is attractive due to its simplicity, but its applicability to electrically driven LEDs is questionable as it cannot account for the complexity of carrier cross-well transport in disordered InGaN, 8,9 which makes the N distribution within an LED unclear. On the other hand, the standard ABC model with only slight modifications ( e.g.…”