This study reports on photoelectrical performance of the long-wave infrared HgCdTe high operating temperature (200–230 K) detector for the fast response time operating under unbiased conditions. The detailed analysis of the response time as a function of device architecture was conducted pointing out optimal working conditions and structure. The response time of the long-wave (x Cd = 0.19) HgCdTe detector for temperatures reached by thermoelectrical cooling (200–230 K) was estimated at the level of τ s < 0.6 ns for unbiased condition while responsivity Ri ∼ 1.8 A/W and detectivity was assessed at the level of D * ∼ 1.6 × 1010 cm Hz1/2/W. It was shown that extra series resistance R series < 10 Ω (resistance–capacitance time constant) plays a decisive role in order to reach τ s < 1 ns meaning that device processing is much more important rather than fundamental limitations imposed by physics.