TECHNOLOGY LEDs
France. For simplicity, we assume that all expelled carriers are hurled out of the entire device [4] – this is modelled by assuming that each Auger event in the quantum well contributes one carrier to the leakage current (Figure 3), which we refer to as Auger leakage.
One of the consequences of this assumption is that Auger effects increase the rate of carrier removal from the well by 50 percent. What’s more, the expelled carriers re-appear as a leakage current component. Add up these two loss channels and it seems that the impact of the Auger effect is increased by a factor of two. Or, to put it another way, once Auger leakage is included, the Auger coefficient can be halved to match measurement data.
Lab Fab ad 28/6/11 12:16 Page 1
Impact of Auger leakage We have built these Auger-related effects into a computer model, which is used to fit real data of a GaN-based, green, single-quantum-well LED [5]. Simulation parameters are determined with Auger leakage turned on, and for comparison, we have also turned Auger leakage off while keeping all other parameters constant (see Figure 4). In both cases, the overlap integral is used in the calculation of Auger recombination in the quantum well. It is worth
noting that when Auger leakage is turned off, the IQE maximum exceeds the corresponding measurement data by 7 percent. To match the experimental data in this case, the Auger coefficient would need to be increased by a factor of two. In other words, with our model a smaller Auger coefficient is needed to explain measurement data, and ultimately the gap between calculated and experimentally extracted Auger coefficients may be significantly smaller than many have thought it to be. The same applies to blue GaN LEDs. So it may be that we are on the right track to uncovering the cause of droop, if we search for its origin by considering both the Auger effect and carrier leakage.
© 2013 Angel Business Communications. Permission required.
References [1] J. Iveland et. al. Phys. Rev. Lett. 11 177406 (2013) [2] J. Piprek et. al. Phys. Status Solidi A 207 2217 (2010) [3] M. Deppner et. al. Proc. SPIE 8619, Physics and Simulation of Optoelectronic Devices XXI, 86191J (2013)
[4] Deppner et. al. Phys. Status Solidi RRL 6 418–420 (2012) [5] Laubsch et. al. IEEE Transactions on Electron Devices 57 79 (2010)
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