The quantum cascade detector is a photovoltaic inter-subband transition infrared detector. Through the cascading subband in the chirped quantum well with gradient thickness, a built-in electric field is generated to transport the photo-generated carriers in the active region. No bias voltage is applied when the device is working, thus avoiding the generation of dark current noise, and achieving room temperature long-wave infrared response. Due to the low absorption coefficient of the inter-subband transition and polarization selection rule, quantum cascade detectors currently have several problems such as low responsivity, no response to normal incidence, and temperature sensitivity of the detectivity. To address these issues, three quantum cascade detectors with new active regions are introduced, including quantum dot/well hybrid, bound-to-miniband diagonal transition, and mini-step transport active regions, exhibiting improved performance for mid, long, and very long wavelength infrared detection.