Info
Info
News Article

Koreans Slam Auger As The Primary Cause Of LED Droop

A Korean partnership has joined the controversial debate over the origin of LED droop. It claims that its sophisticated approach to curve fitting of experimental data demonstrates that Auger recombination only makes a small contribution to droop, the decline in GaN LED external quantum efficiency at higher current densities.
This team from Inha University and Hanyang University arrived at this conclusion by manipulating the standard rate equations, and reducing fit parameters from three to just one. Selecting a suitable value for the Shockley-Read-Hall (SRH) non-radiative recombination coefficient generated a value for Auger recombination (the non-radiative interaction of an electron, a hole, and a third carrier) that is substantially different from that quoted by those backing Auger as the cause of LED droop.



To slash the number of fit parameters to just one, the researchers assumed an injection efficiency of 100 percent.



In addition, they exploited the fact that the gradient of the peak of the internal quantum efficiency as a function of drive current is zero at the maximum value for efficiency.This allowed the construction of new equations that related the rates for SRH recombination, bimolecular radiative recombination, and Auger recombination to the quantum well thickness and the maximum values for current density and internal quantum efficiency.



Experimental results were obtained by taking a 460 nm LED produced by a domestic supplier, and measuring its internal quantum efficiency as a function of drive current. This supplier also provided a value for the quantum well thickness, and the researchers determined the non-radiative carrier lifetime from time-resolved photoluminescence measurements. Lead author Han-Youl Ryu says that this type of photoluminescence measurement could not be used on the LED chips. “Instead, we performed the measurement on an LED wafer with similar layer structures, and estimated the nonradiative carrier lifetime to be about 50 ns."



The researchers then deduced an Auger recombination rate of 10-27 cm6/s, by assuming a maximum internal quantum efficiency of 79 percent, and determining the value for the SRH recombination rate from the non-radiative carrier lifetime measurements.



This value for the Auger recombination rate is at least 1000 times higher than that quoted by other groups that claim Auger is the primary cause of droop, and implies that an alternative non-radiative mechanism is needed to account for declining LED efficiencies at high drive currents.


AngelTech Live III: Join us on 12 April 2021!

AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST) and will feature online versions of the market-leading physical events: CS International and PIC International PLUS a brand new Silicon Semiconductor International Track!

Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.

2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.

We shall also look at microLEDs, a display with many wonderful attributes, identifying processes for handling the mass transfer of tiny emitters that hold the key to commercialisation of this technology.

We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.

Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.

Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.

So make sure you sign up today and discover the latest cutting edge developments across the compound semiconductor and integrated photonics value chain.

REGISTER FOR FREE

VIEW SESSIONS

Info
×
Search the news archive

To close this popup you can press escape or click the close icon.
×
Logo
×
Register - Step 1

You may choose to subscribe to the Compound Semiconductor Magazine, the Compound Semiconductor Newsletter, or both. You may also request additional information if required, before submitting your application.


Please subscribe me to:

 

You chose the industry type of "Other"

Please enter the industry that you work in:
Please enter the industry that you work in:
 
X
Info
X
Info
{taasPodcastNotification}
Live Event