Ga In As P layers and Ga As P/(Al) Ga In P laser diodes(LDs) have been grown on Ga As substrates by metalorganic chemical vapor deposition. The Ga In As P layer, which is lattice matched to Ga As, has an intermediate band gap between Ga0:5In0:5P and Ga As. The Ga In P/Ga As heterojunction spikes, especially in the valence band,can be suppressed by introducing this thin Ga In As P layer into the heterostructure interface. The 808 nm Ga As P/(Al)Ga In P LDs with Ga In As P intermediate layer show a reduced operating voltage compared to the conventional LDs with abrupt Ga In P/Ga As interface due to the enhanced hole injection. As a result, the power conversion efficiency is improved from 52% to 60% at 350 m W output power. At high current injection, the LD with Ga In As P intermediate layer has higher light power owing to the decreased joule heating. Ga In As P layers and Ga As P / (Al) Ga In P laser diodes (LDs) have been grown on Ga As substrates by metalorganic chemical vapor deposition. The Ga In As P layer, which is lattice matched to Ga As, has The intermediate band gap between Ga0: 5In0: 5P and GaAs. The Ga In P / GaAs heterojunction spikes, especially in the valence band, can be suppressed by introducing this thin Ga In As P layer into the heterostructure interface. The 808 nm Ga As P / (Al) Ga In P LDs with Ga In As P intermediate layer show a reduced operating voltage compared to the conventional LDs with abrupt Ga In P / Ga As interface due to the enhanced hole injection. As a result, the power Conversion efficiency is improved from 52% to 60% at 350 mW output power. At high current injection, the LD with Ga In As P intermediate layer has higher light power due to the decreased joule heating.