Strain-balanced InGaN/GaN multiple quantum wells

Abstract

InGaN/GaN multiple quantum well (MQW) structures suffer from a high amount of compressive strain in the InGaN wells and the accompanied piezoelectric field resulting in both a blue shift in emission and a reduction of emission intensity. We report the growth of InxGa1−xN/GaN “strain-balanced” multiple quantum wells (SBMQWs) grown on thick InyGa1−yN templates for x > y by metal organic chemical vapor deposition. SBMQWs consist of alternating layers of InxGa1−xN wells and GaN barriers under compressive and tensile stress, respectively, which have been lattice matched to a thick InyGa1−yN template. Growth of the InyGa1−yN template is also detailed in order to achieve thick, relaxed InyGa1−yN grown on GaN without the presence of V-grooves. When compared to conventional InxGa1−xN/GaN MQWs grown on GaN, the SBMQW structures exhibit longer wavelength emission and higher emission intensity for the same InN mole fraction due to a reduction in the well strain and piezoelectric field. By matching the average lattice constant of the MQW active region to the lattice constant of the InyGa1−yN template, essentially an infinite number of periods can be grown using the SBMQW growth method without relaxation-related effects. SBMQWs can be utilized to achieve longer wavelength emission in light emitting diodes without the use of excess indium and can be advantageous in addressing the “green gap.”

Internal quantum efficiency improvement of InGaN/GaN multiple quantum well green light-emitting diodes

“…D.M. Van Den Broeck et al reported the growth of In x Ga 1−x N/GaN "strainbalan− ced" multiple quantum wells (SBMQWs) grown on thick In y Ga 1−y N templates for x > y [45]. The SBMQW has been a lattice matched to the thick In y Ga 1−y N template.…”

Quantum confinement in transition metal oxide quantum wells

“…Despite their appeal, however, the materials have several problems that hinder their advancement. Among those are the high lattice mismatch between InN and GaN, 17 and large internal fields in the (0001)-oriented (polar direction) multiple quantum well structures. 18 Both lead to reduction of radiative recombination and emission intensity.…”

Integrating AlInN interlayers into InGaN/GaN multiple quantum wells for enhanced green emission

“…The performance of the conventional MQWs shown above is typical for the employed recipe and reactor, and the comparisons show in this letter provide a reasonable metric for improvement. However, it has been shown that AlGaN ILs provide marked improvement over conventional MQWs emitting in the red-green [25][26][27][28][29][30] and given that the AlInN IL MQWs shown here have similar performance to AlGaN IL MQWs is an indication that they too could provide large improvements for long wavelength InGaN MQWs.…”

“…7,8 The efficiency reduction in InGaNbased MQWs emitting in the green-red is attributed to multiple reasons including phase separation in high In-content InGaN; 10,11 defects induced by strong lattice mismatch strain; [12][13][14] low growth temperatures in order to incorporate higher In-concentration that introduces impurities and defects; 15,16 and charge separation caused by strong, built-in polarization fields. [17][18][19] Several solutions have been proposed to enhance the efficiency of green-and red-emitting InGaN-based MQWs, including the use of large overlap QW active regions, [18][19][20][21] non-and semi-polar QWs, 22,23 ternary substrates, 24,25 and AlGaN interlayers (ILs) in InGaN MQW. [26][27][28][29][30][31] Specifically, AlGaN tensile barriers or ILs provide various benefits for higher efficiency green-red LEDs.…”