Physics‐based modeling and experimental implications of trap‐assisted tunneling in InGaN/GaN light‐emitting diodes

Abstract

In a combined experimental and numerical investigation, we present the effects of trap-assisted tunneling on the sub-threshold forward bias characteristics of a blue InGaN/GaN single-quantum-well LED test structure grown on a SiC substrate. The different role of donor- and acceptor-like traps has been studied, for the information it can provide on the role played by point defects. Using the energy Et and trap density Nt as the only tunneling-related fitting parameters, the behavior of the measured I(V) curves is well reproduced by our model over a wide current and temperature range. The very good agreement between simulations and experiments suggests that trap-assisted forward tunneling is one of the most relevant contributions to the current flow below the optical turn-on of the diode

Properties of Defective Regions Observed by Photoluminescence Imaging for GaN-Based Light-Emitting Diode Epi-Wafers

“…In the range of the forward bias at which tunneling occurred, SRH nonradiative recombination was the dominant process in the LED operation. The result was consistent with the reports on trap-assisted tunneling, which employed SRH recombination in the models [17][18][19]. As the DSDRs have a high density of nonradiative recombination defects, which affect the chip operation, the adoption of the PL imaging technique to detect DSDRs can provide an effective inspection and a quick evaluation of LED epi-wafers, allowing the estimation of the properties of the LED chips fabricated from the epi-wafers.…”

“…Their result suggested that a high dislocation density could be the reason for the high ideality factors. Recently, forward leakage at low and intermediate bias region has been explained considering trap-assisted tunneling [13,[17][18][19]. The results in this work indicate that the DSDRs in LED-4 are regions of high density of dislocations and deep traps, which cause the forward leakage.…”

“…Huge forward leakages up to the intermediate bias region (~1.2-1.9 V) were observed for the chips with DSDRs. Many researches on leakages of nitride based LEDs reported that the leakages resulted from the defects present in the active regions [16][17][18][19][20][21]. Several research groups have studied the abnormality of the I-V curve by employing equivalent-circuit models incorporating a parallel resistance and a parasitic diode [14,[21][22][23].…”

“…Tunneling is another important cause of the forward leakage [17][18][19][20][21]. A parasitic diode-like tunnel current at the low-to-intermediate bias deforms the I-V curves from their typical shapes.…”

On the Monte Carlo Description of Hot Carrier Effects and Device Characteristics of III‐N LEDs

“…[10][11][12][13]), which cannot genuinely account for hot carriers and generally also produces larger turnon voltages for MQW LEDs than observed experimentally. [14] Many reasons have been suggested to explain this discrepancy, including charge transport through indium fluctuations, [15] V-shaped pits, [16] tunneling through traps [17] or hot carrier transport. [18] At present it is, however, unclear if the discrepancy is of a physical origin or if it arises simply because the very foundations of the widely adopted DD model make it incapable of predicting the most essential device-level characteristics of LEDs.…”