Normal incidence long-wave infrared InAs/In/sub 0.15/Ga/sub 0.85/As DWELL detectors operating at 8.2 /spl mu/m

The self-assembled InAs/GaAs quantum dot system is grown by molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD). The intersubband and the bound to continuum spacing between the particle-in-a-box like energy levels in these dots lie in the range of 60-450meV (3-12 /spl mu/m). In contrast to the quantum well infrared photodetectors (QWIPs), QD detectors can detect normal incidence radiation due to the absence of a polarization selection rule, making them attractive for large area focal plane array applications. In the past few years, QD detectors have demonstrated very promising device performance. To further improve the device performance and to reduce the dark current in QD detectors, the InAs dots were placed in an InGaAs well. The use of this dots-in-a-well (DWELL) heterostructure lowers the effective bandgap of the InAs dots (in comparision to InAs dots in a GaAs matrix). This leads to an increase in the effective barrier seen by the carriers in the dots, which results in reduced thermionic emission.

Mid-infrared detectors are in great need for a variety of applications such as night vision cameras, remote sensing, medical diagnostics and other atmospheric applications, The main problem with the present day detectors is that they need to be cooled to liquid nitrogen temperatures to avoid the deleterious effects arising from a large dark current at high temperatures. A high detectivity , air-cooled mid-IR detector is highly desirable for all the abovementioned applications. Novel photonic materials are currently being investigated for alternative technologies.