We present a theoretical investigation of a novel staircase-like quantum well infrared photodetector (QWIP). It detects wavelengths between 8.8 mu m and 12.3 mu m at an applied electric field of F= 6 x 10(4) V/cm at room temperature. Device operation is based on inter-subband bound to continuum transition. We also calculated the responsivity at room temperature and dark current density at 77 K. The dark current density was found to be around 10(-8) A/cm(2) at operating bias, which is lower than the conventional QWIPs in the literature. (c) 2005 Elsevier B.V. All rights reserved.