Temperature independence of the droop effect in blue LED's grown on silicon substrates (original) (raw)
Related papers
Investigation of the temperature dependent efficiency droop in UV LEDs
Semiconductor Science and Technology, 2013
The influence of the dislocation density and the carrier-confining potentials on the temperature dependent behavior of the external quantum efficiency (EQE) of near-ultraviolet light-emitting diodes (LEDs) at different current densities has been investigated. The LED efficiencies were found to be very temperature sensitive with characteristic temperatures ranging from 48 to 207 K. In the low current density region the temperature dependence of the EQE is mainly dominated by the Shockley-Read-Hall recombination and hence the dislocation density of the device. In the high current density region, carrier leakage from the quantum wells is the main factor influencing the decrease in the EQE with ambient temperature, and in this region the LEDs become less temperature sensitive with increasing quantum well barrier height.
Efficiency droop suppression in InGaN-based blue LEDs: Experiment and numerical modelling
Physica Status Solidi a-Applications and Materials Science, 2012
In this paper, we report on the results of experimental and theoretical study of a promising way for suppression of the efficiency droop with current in InGaN-based light emitting diodes. Simulations carried out using a drift-diffusion approach with quantum-mechanical corrections clearly show that nonradiative Auger recombination is the principal mechanism limiting the device performance at high-injection level. New design of LED heterostructure with short-period superlattice in the active region is proposed and assessed theoretically. Experimentally, the implementation of the structure design in high-power devices has resulted in substantial suppression of the efficiency droop compared to conventional multiquantumwell InGaN LEDs.
Temperature-dependent internal quantum efficiency of blue high-brightness light-emitting diodes
Internal quantum efficiency (IQE) of a blue high-brightness InGaN/GaN LED was evaluated from the external quantum efficiency measured as a function of current at various temperatures ranged between 13 K and 440 K. Processing the data with a novel evaluation procedure based on the ABC-model, we have determined the temperature dependent IQE of the LED structure and light extraction efficiency of the LED chip. Separate evaluation of these parameters is helpful for further optimization of the heterostructure and chip designs. The data obtained enable making a guess on the temperature dependence of the radiative and Auger recombination coefficients, which may be important for identification of dominant mechanisms responsible for the efficiency droop in III-nitride LEDs. Thermal degradation of the LED performance in terms of the emission efficiency is also considered.
Current crowding effects on blue LED operation
physica status solidi (c), 2006
A hybrid 1D/3D approach to modeling of the electric current spreading in a light emitting diode (LED) die is suggested and validated by comparing the theoretical predictions with available observations. Large-area LEDs with different contact electrode configurations suitable for high-power operation are analyzed in terms of simulations with the focus on the current non-uniformity and its impact on the device electrical and optical characteristics. The factors controlling the LED series resistance are identified by modeling, and ways for the resistance improvement are examined.
Effect of ITO spreading layer on performance of blue light-emitting diodes
physica status solidi (c), 2010
Operation of blue light emitting diodes with ITO spreading layers of various thicknesses deposited on top of the p-contact layer is considered by simulations. Effects of the ITO layer on the current spreading in and the efficiency of light extraction from the LED dice are examined in detail. The electrical LED parameters, operation voltage and series resistance at a certain forward current, are found to be improved with the thickness of ITO films. In contrast, the optical parameters, external quantum efficiency and output power, become reduced with the thickness because of free-carrier light absorption in the ITO films. These opposite trends make practically unrealistic simultaneous optimization of the electrical and optical parameters by varying the ITO layer properties only. An alternative way is suggested for improvement of the LED performance, based on optimization of light extraction from the LED due to a proper choice of the ITO parameters and of current spreading in the die due to an increase of doping level in the n-contact layer.
Applied Sciences, 2019
We compared the efficiency droop of InGaN multiple-quantum-well (MQW) blue light-emitting diode (LED) structures grown on silicon(111) and c-plane sapphire substrates and analyzed the efficiency droop characteristics using the rate equation model with reduced effective active volume. The efficiency droop of the LED sample on silicon was observed to be reduced considerably compared with that of the identical LED sample on sapphire substrates. When the measured external quantum efficiency was fitted with the rate equation model, the effective active volume of the MQW on silicon was found to be ~1.45 times larger than that of the MQW on sapphire. The lower efficiency droop in the LED on silicon could be attributed to its larger effective active volume compared with the LED on sapphire. The simulation results showed that the effective active volume decreased as the internal electric fields increased, as a result of the reduced overlap of the electron and hole distribution inside the qua...
Current spreading and thermal effects in blue LED dice
physica status solidi (c), 2007
We have applied simulations to study current the spreading and heat transfer in blue III-nitride lightemitting diodes (LEDs) with the focus on self-heating and its effect on the device characteristics. A conventional planar design of an LED die is considered for the heat sink through a sapphire substrate. The computations predict a great current crowding at the contact electrode edges, resulting in a non-uniform temperature distribution over the die. The thermal effect on the current-voltage characteristic, output optical power, and series resistance of the diode is analyzed and the theoretical predictions are compared with available observations.
Synergies of controller-based LED drivers and quality solid-state lighting
2006
The present paper emphasizes the importance of electronics and microelectronics towards the future entrance of high-power light emitting diodes (HP-LEDs) in the general lighting market. Electronic controller-based drivers have a key role on the successful and rapid acceptance of solid-state lighting (SSL) products. This paper describes as an example of the SSL potentialities, a LED-base prototype luminaire with adjustable correlated color temperature (CCT) control.
Identification of Auger effect as the dominant mechanism for efficiency droop of LEDs
Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XVIII, 2014
We report on the unambiguous detection of Auger electrons by electron emission spectroscopy from a cesiated InGaN=GaN light-emitting diode under electrical injection. Electron emission spectra were measured as a function of the current injected in the device. The appearance of high energy electron peaks simultaneously with an observed drop in electroluminescence efficiency shows that hot carriers are being generated in the active region (InGaN quantum wells) by an Auger process. A linear correlation was measured between the high energy emitted electron current and the ''droop current''-the missing component of the injected current for light emission. We conclude that the droop phenomenon in GaN light-emitting diodes originates from the excitation of Auger processes.
Scientific Reports
Commercial light emitting diode (LED) materials - blue (i.e., InGaN/GaN multiple quantum wells (MQWs) for display and lighting), green (i.e., InGaN/GaN MQWs for display), and red (i.e., Al0.05Ga0.45In0.5P/Al0.4Ga0.1In0.5P for display) are evaluated in range of temperature (77–800) K for future applications in high density power electronic modules. The spontaneous emission quantum efficiency (QE) of blue, green, and red LED materials with different wavelengths was calculated using photoluminescence (PL) spectroscopy. The spontaneous emission QE was obtained based on a known model so-called the ABC model. This model has been recently used extensively to calculate the internal quantum efficiency and its droop in the III-nitride LED. At 800 K, the spontaneous emission quantum efficiencies are around 40% for blue for lighting and blue for display LED materials, and it is about 44.5% for green for display LED materials. The spontaneous emission QE is approximately 30% for red for display ...