Comparison of structural and optical properties of blue emitting In_0.15Ga_0.85N/GaN multi-quantum-well layers grown on sapphire and silicon substrates

Six periods of 2-nm-thick In _0.15 Ga _0.85 N/13-nm-thick GaN blue emitting multi-quantum-well (MQW) layers are grown on sapphire (Al ₂ O ₃ ) and silicon (Si) substrates. X-ray diffraction, Raman spectroscopy, atomic force microscopy, temperature-dependent photoluminescence (PL), Micro-PL, and time-resolved PL are used to compare the structural and optical properties, and the carrier dynamics of the blue emitting active layers grown on Al ₂ O ₃ and Si substrates. Indium clustering in the MQW layers is observed to be more pronounced on Al ₂ O ₃ than those on Si as revealed through investigating band-filling effects of emission centers, S-shaped peak emission energy shifts with increasing temperature, and PL intensity-peak energy spatial nonuniformity correlations. The smaller indium clustering effects in MQW on Si are attributed to the residual tensile strain in the GaN buffer layer, which decreases the compressive strain and thus the piezoelectric polarization field in the InGaN quantum wells. Despite a 30% thinner total epitaxial thickness of 3.3 μm, MQW on Si exhibits a higher IQE than those on Al ₂ O ₃ in terms of internal quantum efficiency (IQE) at temperatures below 250 K, and a similar IQE at 300 K (30% vs 33%). These results show that growth of blue emitting MQW layers on Si is a promising approach compared to those conventionally grown on Al ₂ O ₃ .