Single layer antireflection coatings have been studied for optimization InGaAs/InP photodetector with normal incident light over the 1300-1550-nm wavelength range. Silicon nitride coatings with various thicknesses were fabricated using plasma enhanced chemical vapor deposition and inductively coupled plasma chemical vapor deposition. The antireflection coating with thickness of 200 nm demonstrated reflection below 10 % at 1550 nm wavelength.