The sensitivities of an aluminum gallium arsenide Al 0.7 Ga 0.3 As-based surface plasmon resonance (SPR) sensor with gold (Au) and silver (Ag) layers are numerically analyzed and compared at 633 nm wavelength for different thicknesses of the Al 0.7 Ga 0.3 As. As the thickness of Al 0.7 Ga 0.3 As increases, the sensitivity of aluminum gallium arsenide Al 0.7 Ga 0.3 As with a specific metal (Au or Ag) layer increases. Our calculations show that the sensitivities of the proposed sensors are 80.55% (Au film) and 34.74% (Ag film) higher than the conventional Au and Ag sensors successively. The aluminum gallium arsenide Al 0.7 Ga 0.3 As-based SPR sensor has the advantages of high angular sensitivity, narrow resonance widths, and low minimum reflectance, making it a much better choice for biosensing applications.