Tunable Bandwidth Quantum Well Infrared Photo Detector (TB-QWIP)

In this thesis a tunable bandwidth quantum well photo-detector (TB-QWIP) is fabricated and experimentally characterized. The designed detector is based on the Stark effect with two quantum step wells arranged opposite to each other to simultaneously achieve both blue- and red-shift of the absorption peak for either direction of the bias. The characterization of the TB-QWIP is based on absorption measurement with Fourier Transform Infra Red (FTIR) spectroscopy, current versus applied voltage (I-V) measurement with a semiconductor parameter analyzer, and photocurrent spectroscopy. The measured IR absorption peaks found at room temperature 8.8 μ m and 10.0μ m are in good agreement with designed values. The dark current of the test detector was found to be 10-9 A and a background photocurrent was found to be 700 x 10-9 A at -4 V bias at 10 K. The background-limited performance of the device was found to be at 60 K. The peak responsivity of the detector was 0.39 A/W at 8.2 μm. The maximum normalized detectivity under background limited conditions D*BLIP, was calculated to be 3.5 x 1011 cm Hz /W . The bandwidth of the detector tuned with bias from 1.8 μm at -1 V to 2.7 μm at -4 V, which amounts to 50% higher than the original width. Further tuning of TB-QWIP parameters based on the analysis of this thesis hold promise for 100% increase of peak width by an applied bias.