Red emission from Eu-doped GaN luminescent films grown by metalorganic chemical vapor deposition

Bright red emission has been obtained at room temperature from Eu-doped GaN films pumped by 325 nm HeCd laser. The luminescent films were grown by metalorganic chemical vapor deposition on $GaN/Al2O3$ substrates. Trimethylgallium (TMGa), ammonia $(NH3),$ and europium 2,2,4,4-tetramethyl-3,5-heptanedionate were used as sources for Ga, N, and Eu dopant, respectively. The influence of the V/III ratio during growth on the photoluminescence (PL) intensity has been studied using a fixed TMGa flow rate of 92 μmol/min and varying the $NH3$ flow rate. The film growth rate (∼2 μm/h) is nearly constant with V/III ratio over the range from ∼30 to ∼1000. The Eu incorporation in GaN films was found to decrease with increasing V/III ratio. The Eu PL intensity (normalized to the Eu concentration) exhibited a maximum at a V/III ratio of ∼100.