Highly sensitive hydrogenated amorphous silicon (a-Si:H) microbolometer arrays have been developed that take advantage of the high temperature coefficient of resistance (TCR) of aSi:H and its relatively high optical absorption coefficient. TCR is an important design parameter and depends on material properties such as doping concentration. Ultra-thin (∼2000 Å) aSiNx:H/a-Si:H/ a-SiNx:H membranes with low thermal mass suspended over silicon readout integrated circuits are built using RF plasma enhanced chemical vapor deposition (PECVD) and surface micromachining techniques. The IR absorptance of the bolometer detectors is enhanced by using quarter-wave resonant cavity structures and thin-film metal absorber layers. To ensure high thermal isolation the microbolometer arrays are vacuum packaged using wafer level vacuum packaging. Imaging applications include a 120×160 a-Si:H bolometer pixel array IR camera operating at ambient temperature. Non-imaging applications are multi-channel detectors for gas sensing systems.