AlN interlayer-induced reduction of dislocation density in the AlGaN epilayer

The emerging ultrawide-bandgap AlGaN alloy system holds promise for the development of advanced materials in the next generation of power semiconductor and UV optoelectronic devices. Within this context, heterostructures based on III-nitrides are very popular in view of their applications as electronics and optoelectronics components. AlGaN-based deep UV emitters are gaining visibility for their disinfection capabilities. Likewise, high electron mobility transistors are attracting increasing attention owing to their superior electron transport which yields high-speed and high-power applications. Those devices are conventionally made of AlGaN/GaN heterostructures grown on foreign substrate. However, structural defects, including stress induced by a mismatch in unit cell parameters and the presence of dislocations, can not only decrease the efficiency of the light emitters (by facilitating the non-radiative recombination of electron-hole pairs), but also impede electron mobility within the two-dimensional electron gas at the AlGaN/GaN interface. Therefore, the significance of obtaining high-quality AlGaN layers becomes evident. Including a thin AlN interlayer between the GaN buffer layer and AlGaN is a possible answer to address these drawbacks. Not only we show that a thin AlN layer, approximately ≤ 3 nm in thickness, between the GaN buffer and AlGaN layers, is effective in decreasing the dislocation densities in the AlGaN layer. Still, this is responsible of an increase in the electron mobility of the resulting heterostructure compared to a classical AlGaN/GaN heterostructure.