Long wavelength infrared absorption characteristics of an In 0 . 3 Ga 0 . 7 As/GaAs quantum well infrared photodetector (QWIP) employing an n-i-p-i-n camel diode structure were compared with those of a conventional n-QWIP. The QWIPs showed a photocurrent response peak at the wavelength of approximately 10 μm due to electronic intersubband transitions in quantum wells. The QWIP employing the camel diode structure showed a reduced dark current, an increased responsivity, and thus an improved detectivity compared with those of the conventional n-QWIP due to the presence of the n-i-p-i-n camel barrier. The results indicated the potential of the QWIP employing an n-i-p-i-n camel diode structure for use in infrared detectors operating at elevated operating temperature.