High temperature annealing on vertical p-n junction p-NiO/n-β-Ga2O3 nanowire arrays for high performance UV photodetection

The authors of this article reported the effects of annealing on performance of GLAD synthesized vertical p-NiO/n-β-Ga2O3 heterostructure (HS) nanowire (NW) arrays based UV photodetector (PD). The authors further investigated the structural, optical and electrical properties at various annealing temperatures (200 °C, 400 °C, 600 °C, 800 °C, and 1000 °C) including as deposited sample to find the best sample for UV PD application. The XRD analysis showed improved crystallinity and least dislocation density and micro strain values for 800 °C sample. However, the sample degrades beyond 800 °C owing to crystallographic defects that are formed at higher annealed temperatures. Furthermore, the photoluminescence analysis showed that the defect levels decreased at 800 °C annealed temperature which was also analogous to the XPS analysis. The FE-SEM analysis also showed the impact of high temperature annealing (800 °C) with increased in nanowire diameter and length. The surface roughness was also found to be smoother for 800 °C sample from TEM analysis. Moreover, the fabricated 800 °C annealed vertical p-NiO/n-β-Ga2O3 axial NW arrays based UV PD showed the largest responsivity (Rλ) of 940 A/W as compared to all the samples. Also, the 800 °C annealed UV PD exhibited fast response speed along with rise time and fall times of 0.32 s and 0.49 s respectively. The superior performance of 800 °C sample was ascribed to the large grain size, defect reduction and improvement of interference quality.