Polarization modification in InGaN/GaN multiple quantum wells by symmetrical thin low temperature-GaN layers

Abstract

Articles you may be interested inThe effect of silicon doping in the barrier on the electroluminescence of InGaN/GaN multiple quantum well light emitting diodes Carrier recombination mechanisms in nitride single quantum well light-emitting diodes revealed by photo-and electroluminescence J. Appl. Phys.Light emitting diodes ͑LEDs͒ using InGaN/GaN quantum wells ͑QWs͒ with thin low temperature GaN ͑LT-GaN͒ layers bounding each InGaN layer are grown by metal-organic vapor phase epitaxy. The light output power of such LEDs increases by a factor of 2 at a drive current density of 35 A / cm 2 compared to that from reference LEDs without the LT-GaN. The blueshift in the emission wavelength is 5.2 nm when the current density increases from 3 to 50 A / cm 2 , which is much smaller than the shift 8.1 nm from reference LEDs. Moreover, the efficiency droop at high current injection is also reduced by 28%, and current density at which peak efficiency is observed increases from 1 to 2 A / cm 2 . High resolution transmission electron microscopy of the QWs bounded with LT-GaN shows higher quality and less strain compared to the reference samples. The better performance of LEDs incorporating the LT-GaN layers is attributed to suppressed polarization from piezoelectric fields.

Improvement of structural and luminescence properties in InGaN/GaN multiple quantum wells by symmetrical thin low temperature-GaN layers

“…It is very close to the design value. The additional LT-GaN with rough 0.5 nm thickness was also observed in the high resolution transmission electron microscope (HRTEM) as we have reported elsewhere [7].…”

“…The other MQWs (designated the 'sandwiched MQWs') wafer had almost the same epitaxial structure except for the active region layers, where every InGaN well is bounded by symmetrical thin LT-GaN layers of 0.5 nm nominal thickness. The detailed growth condition is given in more detail elsewhere [7]. The growth temperature alternated between two different setpoint temperatures.…”

“…The underneath LT-GaN layer may play an important role on the growth of InGaN QW. Recently, we reported the structures of InGaN QWs bounded by symmetrical thin LT-GaN layers, and found the strain in the InGaN QWs was partly relaxed and efficiency droop was improved [7]. The role of the underneath LT-GaN layer on the growth of InGaN QW and the carrier recombination was not reported in detail in that work.…”

“…The LT-GaN barriers prevent the In desorption and relax some strain by crystal lattice deformation, but the quality of the InGaN/ GaN MQWs is not high due to the LT growth of GaN barriers, which will hinder further improvement of device performances. Some groups have used the two step barriers growth to improve the performance of LED [4][5][6][7]. Previously thin LT-GaN layers have been grown before HT-GaN barrier to protect the InGaN well and enhance the quantum efficiency [4,5].…”

Advantage of dual wavelength light-emitting diodes with dip-shaped quantum wells

“…A well-known fundamental problem is referred to as efficiency droop [3][4][5]. The polarization field is widely acknowledged as the main reason for efficiency droop [6][7][8]. The conventional growth direction for GaN-based LEDs is along the polar (0001) axis, and this results in large piezoelectric and spontaneous polarization because of the lack of inversion symmetry [9].…”