Mid Infrared III-V Semiconductor Emitters and Detectors
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A variety of new mid wave infrared (MWIR: 3~5 Μm) and long wave infrared (LWIR: 5~10 Μm) optoelectronic devices have been designed, fabricated, and characterized. Application of the strain engineering and new quinternary material into the active region of light emitting diodes (LEDs) allowed for increasing the internal quantum efficiency more than twofold. InAs/GaSb type II superlattice (SL) active region was used for the LWIR LEDs. It was experimentally demonstrated that only a few periods in the SL contribute to the radiative recombination process, which concludes that active region cascading with fewer periods will be more effective in the LWIR SL LED design. Application of the cascading scheme enabled type I QW Λ=2 Μm LEDs generating record quasi-continuous wave (qCW) power of 10 mW at room temperature. Novel scalable pixel design and fabrication method realized highly dimensional LED arrays with 512 x 512 pixels and the independently controlled dual color LED arrays emitting at 2 Μ m and 3 Μ m. A new precise technique for calibration of LED power has been developed. For lasers, research has been focused on development of single mode tunable lasers. The diode lasers generating 100 mW room temperature CW power at 2 Μm with diffraction limited beam shape have been fabricated using a cost effective wet etching technique. A new principle of laser tuning has been developed using optical pumping. Wavelength of quantum cascade lasers emitting at 9 Μ m was tuned as high as 3 nm at room temperature using optical control of the effective refractive index over the lasing mode. A novel opto-pair scheme for methane detection was designed and demonstrated. The photodetectors with nBn and nBp active region showed the specific detectivity of ~10<super>9</super> cmHz<super>1/2</super>/W at room temperature and were coupled with the LED emitting at 3.3 Μm.