Development of a Low Light Level Solid State Sensor

Image intensifiers based on Negative Electron Affinity (NEA) photocathodes and microchannel plates which are called Generation III image intensifiers suffer from a major limitation of having the long wavelength cutoff only to about 950nm. For that reason, it has poor modulation transfer function and correspondingly lower performance in starlight and in the overcast starlight light levels. To develop a new type of night vision system with much improved capability in the moonless or overcast starlight illumination, a new sensor is needed with long wavelength cutoff extending to about 2m. A focal plane array incorporating a solid state type of detector in a digital camera system will be desirable as it wilt have the ability to integrate with the rest of the digital battlefield of the future. The detectors should be fabricated out of the materials which are amenable to VLSI processing because to compete with the Gen III image intensifier performance an array size of 1024x1024 with detector size of roughly 8m will be required. To fabricate such large size array at reasonable cost, large size wafers (4" or 6") should be processed at a reasonable cost. In this SBIR, PES proposes to develop InGaAs detector arrays with InGaAs layers grown/bonded on GaAs or silicon substrates by special techniques. In addition, PES will incorporate microlenses with the detectors in phase I. Microlenses integrated with the focal plane arrays are found to improve the detector performance very significantly, through improvement of the fill factor, signal to noise ratio and increase of the operating temperature. An 128x128 detector array will be fabricated with the microlenses and tested for its performance in phase I. We propose to develop the InGaAs detector based FPA technology further in phase II to fabricate higher density focal plane arrays, which will be the basis for an extremely high performance low cost night vision system with digital interface and display capability. A helmet mounted system using the InGaAs FPAs will be developed and demonstrated early in phase II. A low cost commercial system will be developed by the end of the program which can be sold in large quantities to the Army and other DoD agencies