Enhanced In incorporation in full InGaN heterostructure grown on relaxed InGaN pseudo-substrate
Abstract
The impact of a relaxed InGaN pseudosubstrate on indium incorporation in a full InGaN heterostructure was investigated. Three types of InGaN pseudosubstrates were tested with different a lattice parameters ranging from 3.190 to 3.205 angstrom, that is to say, greater than that of a GaN template on sapphire. Samples were loaded together in the growth chamber in order to apply exactly the same growth conditions. The effect of the photoluminescence (PL) emission redshift was observed on InyGa1-yN buffer layers and also on InxGa1-xN/InyGa1-yN multiple quantum wells (MQWs). It was found that these pseudosubstrates have the ability to improve the indium incorporation rate, with an increasing effect as the a lattice parameter increases. A strong PL emission redshift was observed in InxGa1-xN/InyGa1-yN MQWs as a function of the increasing a lattice parameter of the InGaN pseudosubstrate, compared to a reference grown on a GaN template. It has been shown that green and amber emissions can be easily reached. A redshift of up to 42 nm was detected between various InGaN pseudosubstrate samples and up to 62 nm compared to a conventional structure emerged from a GaN buffer on the sapphire substrate. The average QW width less than 3 nm indicates a higher In content. The reduced compressive strain originating from the relaxed InGaN substrate allows the reduction in the compositional pulling effect and consequently enables an enhanced In incorporation rate.