An innovative method of fabricating large-area long wavelength infrared (LWIR) detector arrays that can be operated at room as well as cryogenic temperatures is proposed. This technique uses established technologies of micro-machining and microelectronic processing of silicon (Si) wafers for fabricating monolithic arrays of LWIR detectors. The detector elements of the array are formed by an ultra-thin film of a bolometer material possessing the highest temperature coefficient of resistance known, and the readout electronic microcircuit is fabricated on the same silicon chip next to the elements. The resultant detector arrays will possess features of low cost, low weight, high responsivity and high sensitivity. The low cost is due to a monolithic array structure requiring no cooling. The high responsivity is due a large to a large temperature coefficient of resistivity (greater than 15% to 0.2% for a conventional bolometer) of the new bolometer material. The high sensitivity is due to the combined effects of high responsivity, low noise and high thermal isolation of the bolometer from its surroundings.