Cp₂Mg-induced transition metal ion contamination and performance loss in MOCVD-grown blue emitting InGaN/GaN multiple quantum wells

The detrimental effects of Cp 2 Mg-induced trace transition metal (iron and manganese) contamination on the optical performance of metalorganic chemical vapor deposition (MOCVD)-grown blue-emitting InGaN/GaN multiple quantum wells (MQWs) are investigated experimentally. Five samples are grown at various stages of conditioning of a freshly installed MOCVD tool with stainless steel gas lines. Without conditioning, Cp 2 Mg flow induced Fe and Mn impurities with concentrations of 3 × 10 15 and 3 × 10 14 cm-3, respectively. These contaminants introduce nonradiative recombination centers with lifetimes on the order of nanoseconds. These impurities also induce indium-clustering related phenomena such as low energy shoulder at low temperature and a strong S-curve shift in emission energy with increasing temperature. Through successive cycles of chamber conditioning, the Fe and Mn concentrations decrease to below their detection limits, and the nonradiative recombination lifetime (+8 ns), internal quantum efficiency (+26%), microphotoluminescence nonuniformity (-4.7%), and S-curve shift (-26 meV) of the MQWs improved. The suppression of the transition metal ion contamination in the MOCVD chamber is shown to be crucial for high performance MQWs and blue light emitting diode growths.