Current injection efficiency induced efficiency-droop in InGaN quantum well light-emitting diodes

Influence of electron distribution on efficiency droop for GaN-based light emitting diodes

“…But for these applications, LEDs need to be operated at a current density below 10 A/cm 2 because of droop effect, which is still a key problem obstructing the development of high-power lighting-emitting diodes. Till now, lots of mechanisms have already been suggested to explain the "efficiency droop", such as polarization effect [1,2], electron leakage out of the active region [3,4], carrier delocalization [5], carrier injection efficiency [6], Auger recombination [7] and defects [5]. But the physical mechanisms of the droop effect aren't entirely clear and there is still a debate between them.…”

Direct Measurement of Auger Electrons Emitted from a Semiconductor Light-Emitting Diode under Electrical Injection: Identification of the Dominant Mechanism for Efficiency Droop

“…However, the interpretation of the droop phenomenon remains highly controversial, in spite of its importance and many studies. Many proposed mechanisms rely on the enhanced nonradiative (NR) recombination at point defects in either quantum barriers or surrounding majority carrier regions when carriers are no longer localized in the high radiative recombination efficiency regions of quantum wells (QWs): carrier overflow from the QWs into regions of efficient NR recombination [4,5] in particular due to saturation of localized states in the QWs [6]; loss of current injection efficiency [5]; density-activated defect recombination [7]; insufficient hole injection efficiency leading to electron leakage [8]. Auger recombination in the QW is however a somewhat favored mechanism [3], with possibly an early onset induced by the reduction in active volume due to current crowding [9] or by carrier localization [10,11].…”

On the origin of the electron blocking effect by an n-type AlGaN electron blocking layer

“…[1][2][3] The device performance is, however, still limited by Auger recombination, 4,5 charge separation, 6-9 current crowding, [10][11][12] insufficient hole injection, 9,[13][14][15][16][17][18] and electron overflow from the MQW active region. [19][20][21][22] In order to address these issues, a staggered quantum well architecture and also InGaN/GaN MQWs with Si-step-doped quantum barriers have been proposed to screen the quantum confined Stark effect (QCSE) and increase the spatial overlap of electron-hole wave functions, [7][8][9] while an improved current spreading can be obtained either by making the p-type layer more resistive or the p-contact layer more conductive. 10,11 Additionally, an improved crystal quality is also essential for improving the device efficiency.…”

“…Polarization matched p-type electron blocking layer (EBL) and quantum barrier cap layers with a large energy bandgap have been proposed. [19][20][21] However, the p-type electron blocking layer can on one hand reduce the electron overflow, and on the other hand, it also retards the hole injection. 24 Recently, the n-type electron blocking layer has also been demonstrated.…”