We proposed a calculation method for the band alignment of a novel InGaPN/GaPN single-quantum well (SQW) on GaP and Si substrates. The calculation method composed the model-solid theory (MST) for the band edge shifts due to strain and the band anticrossing (BAC) model for a large band bowing of an InGaPN alloy due to N incorporation. The band alignments of the InGaPN/ GaPN SQW with In compositions larger than 27% on GaP and Si substrates were investigated by the calculation method, whose QW could have a direct bandgap. The 18-K experimental photoluminescence (PL) peak energy of the InGaPN/GaPN SQW on a Gap substrate, which was grown by radiofrequency plasma-assisted molecular-beam epitaxy (RF-MBE), was in good agreement with the calculated transition energy between the first electron quantum level and the first heavy-hole quantum level. The conduction band offsets of the InGaPN/GaPN SQW with N compositions of 1-2% into the InGaPN well grown on GaP substrates were several dozens meV at the most, while the valence band offsets were 200-300 meV due to compressive strain increased by increasing In compositions. Therefore, larger N compositions of the InGaPN well were required to increase the conduction band offsets of the InGaPN/GaPN SQW for light-emitting devices. It was demonstrated that the type-I InGaPN/GaPN SQW with a direct bandgap could be obtained on Si substrates. Our calculation results showed that the appropriate In composition of the InGaPN well were 30-45% and N composition of the GaPN barrier 1-2%. The differences of N compositions around 3% between the InGaPN well and the GaPN barrier were required for realizing a conduction band offset of 300 meV. (c) 2006 Elsevier B.V. All rights reserved.