We report the device performance of normal-incidence (In, Ga)As/GaAs quantum dot intersubband infrared photodetectors. A primary intersubband transition peak is observed at the wavelength of 13 &mgr;m(E0→E1)and a secondary peak at 11 &mgr;m(E0→E2).The measured energy spacing in the conduction band of the quantum dots is in good agreement with low temperature photoluminescence measurement and calculations. A peak detectivity of1×1010 cm Hz1/2/Wat 13 &mgr;m was achieved at 40 K for these devices. ©1998 American Institute of Physics.