Implications of changes in the injection mechanisms on the low temperature electroluminescence in InGaN∕GaN light emitting diodes

Abstract

Carrier recombination mechanisms in nitride single quantum well light-emitting diodes revealed by photo-and electroluminescence J. Appl. Phys. 104, 094504 (2008); 10.1063/1.3009335 Temperature dependence of the electrical activity of localized defects in InGaN-based light emitting diodesThe presence of traps is sometimes favorable, and sometimes detrimental to the electrical transport and optical efficiency in III-nitride quantum heterostructures. This work presents the results of a joint analysis of electrical features and electroluminescence in InGaN / GaN-based blue light emitting diodes; a detailed and exhaustive reading of the carrier injection mechanisms highlights the central role of trap centers near the active region. Some suggestions will be eventually advanced as to the design of devices with better emission performances.

Efficiency droop in blue InGaN/GaN single-quantum-well light-emitting diodes on the Si substrate

“…Figure 2 shows the relative IQE of SQW LEDs as a function of forward current density in the temperature range from 100 to 350 K. It can be seen that the IQE increases with decreasing temperature at low forward current density (less than 10 A cm −2 ), but at relatively high forward current density the IQE decreases with the decreasing temperature when the temperature is below 200 K, and the IQE of SQW LEDs at 100 K is even lower than that at 350 K when the forward current density is above 60 A cm −2 . The phenomenon that the quantum efficiency of SQW or multiple quantum well (MQW) LEDs decreases with the decrease of temperature at high-input current density is reported by many research groups [12][13][14], but none of them explained the mechanism.…”

A new approach to correlate transport processes and optical efficiency in GaN-based LEDs

“…For qualitative considerations, a scheme of the typical energy band diagram [19,20] is reported in figure 3. The equilibrium profile (dashed curve), where a huge bending is present from the n-side to the p-side, completely changes when an external electric field is applied by injecting a forward current (solid curve), as in the operating conditions of the diode.…”

“…The EL emission depends on the electron transfer efficiency from the MQW structure to the SQW, occurring probably by means of a trap-assisted path, as hopping/tunnelling of electrons on suitable trap levels in the GaN barrier or an overbarrier flow [20] (arrows in figure 3).…”

“…The activation energy of about 26 for trap M 1 was calculated from the Arrhenius plot EL intensity at 2 mA (not shown here [20]) and it could agree with the TAS level at about 54 meV. The traps associated with M 2 are too deep to be thermally ionized at temperatures at which they are electrically active, so their activation energy is not available but it could be traced back to the traps evidenced by TAS with energies of about 100 and 235 meV.…”

Carrier distributions in InGaN/GaN light‐emitting diodes

“…In light‐emitting diodes (LEDs) containing InGaN/GaN quantum wells (QWs) it is widely believed that injected holes are preferentially captured into the QWs closest to the p ‐type layer. This conclusion has been arrived at based on drift‐diffusion calculations , in which the large effective mass and low diffusivity of the holes result in the holes being preferentially captured by the first few QWs rather than diffusing further into the structure . Some experimental support for this conclusion has been presented by David et al , in which the far‐field illumination pattern of an LED was modelled.…”