A model of barrier-separated regions is proposed that leads to quantization and spatial correlation of carriers near the band gap of hydrogenated amorphous silicon. The size of these regions, which consist of pure Si bounded by potentials emanating from Si-H bonds, is estimated from a classical percolation picture. Near band gap localized states lie in these quantum well regions and are about 0.3 eV more widely separated than in unbounded Si, thereby accounting for a wide variety of hitherto uncorrelated experimental results. Dopants enhance conductivity by providing conduction paths through the barriers. Spatially coincident pairing of conduction with valence band localized states is speculated to be relevant to other amorphous semiconductors as well. © 1980, All rights reserved.