QWIP

X 256, 25 pm pitch two-color QWIP EPA operating at > 70K (MW/LW) and > 65K (LW/LW). Data include graphs of spectral response curves and dark current vs bias. 

Quantum Well IR Photodetector (QWIP) Intraband photoexcitation of electrons horn confined states in the conduction band of quantum wells into the continuum 

See also Gallium entries GaAs-AlGaAs QWIPs, 22 181-182. 

Spatial resolution 1.1 milliradian (320 x 240 element GaAs QWIP FPA) Frame repetition rate selectable from 50/60 Hz to 750/900 Hz 

The newest and perhaps most versatile of the detectors shown is the QWIP array. QWIP detectors are made from gallium arsenide (GaAs) material. These detectors are narrow-band, high-speed, high-sensitivity detectors that can be designed to operate in selected narrow bands from the MWIR (2-5 pm) to the LWIR (8-14 pm). The versatility of this detector, as well as others, will be illustrated in the applications chapters in Part II of this text. 

S. D. Gunapala and S. V. Bandara, Quantum Well Infrared Photodetector (QWIP) Focal Plane Arrays 

Eig. 13. Absorption between confined energy levels in a quantum well infrared photodetector (QWIP). The energy difference between the 

Fig. 13. Absorption between confined energy levels in a quantum well infrared photodetector (QWIP). The energy difference (E —E ) between the confined energy levels in a quantum well may be designed such that it is resonant with ir radiation. The band gap, E is much greater, therefore direct band

AIM pCam, FS, HuntIR, and FL FLIR Families Modular, building block cameras using cooled HgCdTe, GaAs QWIP and PtSi FPAs from 128 x 128 element to 640 X 486 element. 

Early devices using lattice-engineered materials were referred to as quantum well infrared photodetectors (QWIPs), then as quantum dot infrared photodetectors (QDIPs), but now it is difficult to separate them from other natural materials. 

B. F. Levine, Quantum Well Infrared Photodetectors, J. Appl. Phys., 1993, 74, see also S. D. Gunapala, S. V. Bandara Quantum Well Infrared Photodetector (QWIP) Focal Plane Arrays in Semiconductors and Semimetals (2000), V. 62 Chapter 4 (Academic Press). 

For special applications where high speed, improved sensitivity, or spectral selectivity is required, cooled photodetector arrays are used. These include PtSi, InSb, HgCdTe, and most recently GaAs QWIPs, all of which require cooling. The spectral response characteristics of these detectors are illustrated in Fig. 2.16. 

FLIR devices can be divided in two classes by their detecting waveband. Mid-IR detectors, like the StarSAFIRE series mentioned above, are commonly used in humid environments since they show less signal depression by water vapour. However the detection of oil spills shows variable results and is not favourable as a stand-alone sensor for this purpose. Long-IR detectors (8-14 pm, sometimes realised by QWIP detectors with smaller 

---