Photodetectors operating in the mid-infrared (IR) wavelength range (3 – 4 µ m) are widely used in gas analysis instruments and low-temperature pyrometry, such as methane and natural gas sensors, alcohol detectors, fire safety sensors, and fast-response pyrometers. This study investigates the causes of the decrease in current sensitivity with rising temperature in surfaceilluminated photodiodes (PDs) based on n-InAsSbP/InAs/p-InAsSbP double heterostructures (DHS), sensitive in the spectral range of λ = 2 – 4 µm at temperatures of 200–500 K. Proposed design improvements for the PD chip resulted in a weaker temperature dependence of the parameters, enabling reliable operation at 500 K with a current sensitivity of Si = 0.1 A/W.