Molecular beam epitaxial growth and optical characterization of AlGaN nanowires with reduced substrate temperature

The requirement of high growth temperature for high-quality epitaxial AlGaN, which is typically around 100 °C higher than the growth temperature of GaN, is unfavorable for p-type dopant (Mg) incorporation, representing a grand challenge for AlGaN deep ultraviolet (UV) light-emitting devices. In this context, we show high-quality AlGaN nanowires emitting in the deep UV band grown at merely the growth temperature of GaN nanowires by molecular beam epitaxy. This is enabled by the discovery of a narrow GaN nanowire template growth window. We have further compared the room-temperature internal quantum efficiency of the samples emitting around 255 nm grown in the low-temperature regime and high-temperature regime. It is found that the sample grown in the low-temperature regime can possess optical quality close to the sample grown in the high-temperature regime. This study, therefore, suggests that even with a low growth temperature, using nanowire structures can still lead to AlGaN alloys with a relatively high optical quality, and the use of low substrate temperature could be beneficial for p-type doping.