We demonstrated a novel method to grow InGaAsP linear graded-index separate confinement heterostructure (GRINSCH) (lambda=1.05-1.24 mu m) by ramping the growth temperature in the metallorganic chemical vapor deposition system. From secondary ion mass spectroscopy and photoluminescence analysis, the composition of linearly graded In1-xGaxAsyP1-y layer is well in control. By introducing this GRINSCH InGaAsP structure, 1.55-mu m SMQW ridge waveguide laser diodes with a back-facet high-reflection coating exhibit a low threshold current of 6.5 mA at 20 degrees C, a high light output power of 20 mW at 80 mA, and a high slope efficiency of 0.37 mW/mA, also showing potential for high-temperature, continuous-wave operation up to 95 degrees C. The longitudinal mode oscillates at 1.536 mu m at 20 degrees C and the 0.45-nm/degrees C of red-shift rate in wavelength.