N/GaN heterostructures for near-infrared intersubband absorption*

Lattice-matched In_0.17Al_0.83N/GaN heterostructures are promising platforms for near-infrared optoelectronic devices based on intersubband transitions. Previously, strong near-infrared intersubband absorption (ISBA) was demonstrated in InAlN/GaN superlattices. But, reducing compositional inhomogeneity of InAlN barriers and effective doping of these heterostructures that affect ISBA properties presented open challenges. Here, we demonstrate that InAlN/GaN structures with saturated indium composition of 0.17 can be grown by plasma-assisted molecular beam epitaxy over a wide range of growth conditions and constructed the growth diagram for lattice-matched InAlN layers. Our results indicate that the studied growth conditions alone are not sufficient to eliminate the indium segregation and additional mechanisms are involved. The impact of an indium adlayer and a thin AlN nucleation layer on compositional inhomogeneity of InAlN barriers is discussed. We report the impact of different Si doping profiles and doping levels on structural quality and hence ISBA properties of lattice-matched InAlN/GaN superlattices.