Density-activated defect recombination as a possible explanation for the efficiency droop in GaN-based diodes

Abstract

It is shown that a carrier loss process modeling density-activated defect recombination can reproduce the experimentally observed droop of the internal quantum efficiency in GaN-based laser diodes.

Dislocation related droop in InGaN/GaN light emitting diodes investigated via cathodoluminescence

“…Some previous work pointed out that defect recombination could be viewed as consistent with the droop behavior in the LEDs, however. 4,5 At injection conditions close to the peak of the LED efficiency curve (like external quantum efficiency vs current density, often called the LI-curve), the injected carriers are generally viewed as largely localized and, thus, immune to the major non-radiative defect recombination at dislocations. At high injection the localization potentials are screened, and the carriers are free to move to defect sites.…”

Defect recombination induced by density-activated carrier diffusion in nonpolar InGaN quantum wells

“…8 This process is very sensitive to the carrier density but insensitive to the degree of localization. (3) The e-e scattering can drive the carriers cross the barriers as proposed by Hader et al 13,14 This process is temperature insensitive; however, a density threshold is required to ensure the scattering magnitude sufficient to overcome the potential barriers. 14 To confirm the process of DADR and check the major mechanism responsible for defect recombination, we study the PL properties by changing the excitation photon energy and the temperature.…”

“…[1][2][3] In the past decade, multiple mechanisms have been proposed to explain the efficiency droop including Auger recombination induced by multi-particle interactions, [4][5][6][7][8] electron leakage due to poor hole injection and electron overflow, 9,10 carrier loss related to reduction or saturation of carrier localization, 11,12 and other processes including the density-activated defect recombination (DADR). 13,14 Some of these factors have been found to be tightly associated with the internal polarization field. [15][16][17][18][19][20][21] The reduction on internal polarization and the increase of hole concentrations in nonpolar QWs can efficiently suppress the loss during carrier injection.…”

“…4,22 Nevertheless, some recent works have proposed high carrier density may activate the defect-related recombination. 13,14 This process of DADR is predicted to be responsible for the efficiency droop. 18,19 In this letter, we report experimental evidences that the process of DADR can be a major channel responsible for the efficiency droop in nonpolar a-plane InGaN QWs.…”

Self-screening of the quantum confined Stark effect by the polarization induced bulk charges in the quantum barriers

“…On one hand, the crystal quality of the epitaxial LED wafers has room to be further improved, 3 which will help to suppress the carrier loss through the defect-related nonradiative recombination. 4,5 On the other hand, the Auger recombination is rendered as another carrier loss channel in the multiple quantum well (MQW) region. 6,7 Moreover, the InGaN/GaN LEDs grown along [0001] orientation suffer from the strong polarization induced electric fields, and the resulted tilted energy band leads to a spatial separation of the carrier wave functions and thus a reduced radiative recombination rate, known as the quantum confined Stark effect (QCSE).…”