Effect of H₂O intentionally doping on photoelectric properties in MOVPE-growth GaN layers

GaN crystal growth requires higher purity of materials. Some contaminants in NH3 gas could be the causal factor of defects in GaN crystals. These atoms act as donor or acceptor. In order to clearly demonstrate the effect of gaseous impurities such as H₂O on the properties of undoped-GaN layer, high purity NH₃ (N70) was used as NH₃source. The concentration of H₂O in NH₃ was varied at 32, 49, 75, 142, 266, 489, and 899 ppb, respectively. Under the same recipe, we deposited undoped-GaN epitaxial layer with purifier, and H₂O-doped GaN series layers. As similar to the results of CO and CO₂-doped GaN series, the increase tendency of carrier density changing with increasing H₂O concentration. The FWHMs of XRC around (0002) remain stable, witnessing that the crystal quality of GaN layer remain good. LT (15K) PL of undoped-GaN and H₂O-doped GaN were measured, the D⁰X emission peak intensity of all H₂O-doped GaN are decreased drastically compared with undoped-GaN. H₂O impurity was doped into GaN layer, which not only effects electrical properties and but also effects the radiative emission and furthermore effects PL intensity, its mechanism is discussed.