The dependence of the emission from MQWs on the indium content in the underlying InGaN templates: experimental and modeling results

Abstract

The effect of underlying highly relaxed In y Ga1-y N templates on In x Ga1-x N multiple quantum wells (MQWs), where x> y, is investigated. Photoluminescence (PL) measurements and tested light emitting diodes (LEDs) show that relaxed In y Ga1-y N templates with y ∼ 10% can cause a red shift in MQWs emission of Δ E ∼ 0.33 eV . This red shift is attributed to the reduced strain in the MQWs, resulting in a decrease in the MQWs band gap, along with an increase in indium incorporation in the QWs due to composition pulling effect. Theoretical modeling was applied to study the effect of the template’s indium content and its degree of relaxation on the observed red shift in MQW emission. The proposed model uses the PL emission data from the MQW to predict the indium content in the MQWs grown on GaN and on InGaN templates. Using this model, we are able to predict the dependence of both the amount of the red shift and the indium incorporation enhancement in the QWs on the In-content in the underlying templates. We are not aware of any similar modeling activities that reported such predictions. LED devices were fabricated using the In y Ga1-y N templates and compared to conventional LED structure grown on GaN, showing a red shift in electroluminescence that agrees with the PL results.

Reduction of V-pit density and depth in InGaN semibulk templates and improved LED performance with insertion of high temperature semibulk layers

“…However, we suggest a possible source of the droop reduction could be attributed to the reduction of conduction band difference between the active region and the underlying template, when compared to that of GaN, as related to hot carrier injection. Ballistic electrons that are not thermalized and captured by the active region of a device are suspected to contribute to carrier leakage [22]; as electrons from the underlying larger bandgap material (GaN in traditional devices) are injected into the smaller bandgap active region material (InGaN), they gain extra kinetic energy due to the conduction band difference. leads to an increased chance for the electron to bypass, or overfly, the active region.…”

Recent Progress in Long‐Wavelength InGaN Light‐Emitting Diodes from the Perspective of Epitaxial Structure

“…Abdelhamid et al disclosed the dependence of the emission from MQWs on the indium content in underlying InGaN templates grown via semibulk approach. [ 40 ] Compared to GaN template, the relaxed In 0.1 Ga 0.9 N template induced a redshift in emission wavelength up to 62 nm, which was attributed to the reduced strain in MQWs, along with the increased indium incorporation by suppressing composition pulling effect. They further enhanced the indium composition in InGaN template, finding that the redshift of emission wavelength was about 100 nm at the expense of degraded crystal quality.…”