Detection of hot electrons originating from an upper valley at ∼1.7 eV above the Γ valley in wurtzite GaN using electron emission spectroscopy

Using electron emission spectroscopy, measurement and analysis were conducted on the energy distribution of vacuum emitted electrons from electrically driven InGaN/GaN green (peak wavelengths λ≈515nm) light-emitting diodes (LEDs) with and without a prewell superlattice (SL). We report on the detection of a high-energy upper valley at ∼1.7eV above the Γ valley from samples with no prewell SL. We propose that these upper valley electrons originate predominantly from trap-assisted Auger recombination (TAAR) in green LEDs, as the intensity of these peaks is found to have quadratic dependence on the carrier density n [see Espenlaub et al., J. Appl. Phys. 126, 184502 (2019)10.1063/1.5096773]. The high-energy upper valley peak was not observed in the sample with a prewell SL which is attributed to gettering by the prewell SL of still unidentified impurities that act as TAAR centers.