Exclusion of injection efficiency as the primary cause of efficiency droop in semipolar (202¯1¯) InGaN/GaN light-emitting diodes
Abstract
We extract the injection efficiency as a function of current density in single-quantum-well semipolar (202¯1¯) InGaN/GaN light-emitting diodes (LEDs) using small-signal RF measurements and rate equation analysis of the dominant carrier mechanisms. The rate equations are used to derive a small-signal equivalent circuit that yields expressions for the modulation response and the input impedance of the LED. Simultaneous fitting of the modulation response and the input impedance of the circuit to the measured modulation response and the input impedance of the LED gives the differential carrier lifetime, the net differential carrier escape time from the active region, and the differential recombination lifetime in the cladding layers. The extracted lifetimes are used to calculate the injection efficiency of the LED at various current densities. Carrier leakage from the active region results in an injection efficiency below one at low current densities. At high current densities, the injection efficiency approaches one due to the higher recombination rate in the quantum well (QW) and the lower carrier leakage. Analysis of the lifetimes shows that the higher recombination rate in the QW results in a slower increase in the carrier population in the QW compared to that in the cladding layers. However, the recombination current in the QW is generally higher than that in the cladding, leading to high injection efficiency at high current densities. The data are consistent with a Coulomb-enhanced capture process. The high injection efficiency obtained at high current densities rules out injection-related mechanisms as the primary cause of efficiency droop in semipolar (202¯1¯) InGaN/GaN LEDs.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jul 16, 2018
- Source ID
- 10.1063/1.5036761
Entities
People
- Andrew Aragon
- Arman Rashidi
- D. Feezell
- Morteza Monavarian
Organizations
- Army Research Office
- United States Army Research Laboratory
- University of New Mexico