The influence of NH3 Flow Rate on the photoelectric properties of high Al content p-AlGaN

High Al content (60%) p-AlGaN with different NH₃ flow rates was grown using metal-organic chemical vapor deposition (MOCVD), and changes in its photoelectric properties were studied using the Hall effect tester (Hall) and cathodoluminescence (CL) spectrometer. The results show that the film resistivity increases from 3.8Ω·cm to 46.5Ω·cm with increasing NH₃ flow rate. The impurity peak intensity of p-AlGaN grown under high NH₃ flow conditions is particularly high, indicating numerous point defects. The results of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) show a large number of Ga interstitial atoms (Ga_i) at the interface. As Ga_i acts as a donor, this may be the main reason for the increase in resistivity. And under high NH₃ flow conditions, a lattice distortion and a high density of dislocation occur between p-AlGaN and p-GaN, which can lead to enhanced carrier scattering and decreased mobility. Additional validation via LED growth experiments indicates that the luminescence intensity of samples with low ammonia concentration increased by more than 13000 times.