The properties of InGaAs/(100)InP were studied, which is a promising material for the electrical device using its highest room temperature mobility and for the optical device utilizing its long wavelength region($\lambda=1.3-1.55$um) band gap. The growth characteristics were studied experimentally. As grown surface were wavy and partially flat, which were the characteristics of LPE grown layer and were suspected to be due to the ternary-binary interface and long time baking. To make an optical device, the diode was fabricated and tested. To check its electrical properties, I-V and C-V measurements were taken.