The recent progresses of our research in In<sub>x</sub>Al<sub>1-x</sub>Sb infrared detector based on molecular beam epitaxy are presented. Al composition with 0-0.3 is used for adjusting energy gaps of InSb and a p-i-n structure is utilized to decrease dark current. In<sub>x</sub>Al<sub>1-x</sub>Sb ternary alloys are grown by molecular beam epitaxy on InSb substrates, and the material quality is characterized using high resolution x-ray diffraction. In order to exploit this epitaxial material we have developed new mesa and passivation technology based on matured InSb fabrication process. The InAlSb diodes has a cut-off wavelength of around 4.8μm. The reverse bias dark current of InAlSb diodes have been measured. The dark current of the pin InAlSb diode is seen to smaller that of the bulk p<sup>+</sup>n InSb diodes by 4-5 times in 77K.
A multi-element double ring infrared detector based on InSb p-n photodiodes is presented. The presented detector includes an outer ring detector and an inner ring detector. Each ring consist 10 detector elements, five mid-wave infrared detector elements and five short wave infrared detector elements. Two wavebands of 3.5–5 μm and 1.5–3 μm in mid-wave infrared and short wave infrared are adopted. The mid-wave infrared and short wave infrared detector elements are arranged alternately and close to each other to form detection pair. Between the adjacent detector elements, there is an interval to avoid cross talk. Dual band filter thin films are directly coated on the photodiode surface to form a dual band infrared detector. The double ring detector which can perform dual band IR counter-countermeasures can track target effectively under infrared countermeasure conditions.