Impact of crystal orientation on the modulation bandwidth of InGaN/GaN light-emitting diodes
Abstract
High-speed InGaN/GaN blue light-emitting diodes (LEDs) are needed for future gigabit-per-second visible-light communication systems. Large LED modulation bandwidths are typically achieved at high current densities, with reports close to 1 GHz bandwidth at current densities ranging from 5 to 10 kA/cm2. However, the internal quantum efficiency (IQE) of InGaN/GaN LEDs is quite low at high current densities due to the well-known efficiency droop phenomenon. Here, we show experimentally that nonpolar and semipolar orientations of GaN enable higher modulation bandwidths at low current densities where the IQE is expected to be higher and power dissipation is lower. We experimentally compare the modulation bandwidth vs. current density for LEDs on nonpolar (101¯0), semipolar (202¯1¯), and polar 0001 orientations. In agreement with wavefunction overlap considerations, the experimental results indicate a higher modulation bandwidth for the nonpolar and semipolar LEDs, especially at relatively low current densities. At 500 A/cm2, the nonpolar LED has a 3 dB bandwidth of ∼1 GHz, while the semipolar and polar LEDs exhibit bandwidths of 260 MHz and 75 MHz, respectively. A lower carrier density for a given current density is extracted from the RF measurements for the nonpolar and semipolar LEDs, consistent with the higher wavefunction overlaps in these orientations. At large current densities, the bandwidth of the polar LED approaches that of the nonpolar and semipolar LEDs due to coulomb screening of the polarization field. The results support using nonpolar and semipolar orientations to achieve high-speed LEDs at low current densities.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jan 22, 2018
- Source ID
- 10.1063/1.5019730
Entities
People
- Andrew Aragon
- Arman Rashidi
- Ashwin K. Rishinaramangalam
- D. Feezell
- Morteza Monavarian
- S. H. Oh
- Steven P. DenBaars
Organizations
- National Science Foundation
- Solid State Lighting and Energy Electronics Center, University of California Santa Barbara
- United States Department of Defense
- University of New Mexico