Metal-oxide-semiconductor tunneling diodes can be used as photodetectors; at the inversion bias. To increase the responsivity, delta-doping is used in the quantum dot infrared photodetectors (QDIPs) and quantum well infrared detectors (QWIPs). The peak responsivity of the quantum dot and quantum well infrared photodetector at 15 K is found to be 0.03 mA/W and 1.3 mA/W, respectively, at a gate voltage of 1 V. The higher responsivity of the QWIP is probably due to the continuous two-dimensional density of states and smaller transition energy as compared to the QDIP. The QD photoresponse in the peak wavelength range 3.5-5 mu m can be measured up to 100 K, while that for QW 3-7 mu m can only be detected up to 60 K. A higher dark current due to the lower transition energy in the QWIP limits its operating temperature as compared to the QDIP. (c) 2005 Elsevier B.V. All rights reserved.