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

The effect of underlying highly relaxed In_yGa_1-yN templates on In_xGa_1-xN multiple quantum wells (MQWs), where x> y, is investigated. Photoluminescence (PL) measurements and tested light emitting diodes (LEDs) show that relaxed In_yGa_1-yN templates with y ∼ 10% can cause a red shift in MQWs emission of $\Delta E\sim 0.33\text{eV}$. 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_yGa_1-yN templates and compared to conventional LED structure grown on GaN, showing a red shift in electroluminescence that agrees with the PL results. (paper)