We report on reverse biased photoconductive detectors with novel design and improved high‐frequency performance. Taking advantage of the ‘‘giant ambipolar diffusion constant’’ which has been observed previously inn‐i‐p‐idoping superlattices very fast carrier transfer from the inner absorption area to the outer detection area is achieved. The combination of narrow contact spacings and smallRCand diffusion time constants results in very high gain‐bandwidth products (≳20 GHz) with adjustable 3 dB frequencies. ©1995 American Institute of Physics.