A grossly inhomogeneous, noncolumnar morphology has been observed in doped, plasma‐deposited hydrogenated amorphous silicon (a‐Si:H) within critical ranges of the diborane to silane ratio in the gas phase. The diborane level can be as low as 5 ppm and depends both on the electrode self‐bias potential and the growth rate. Undoped specimens prepared under the same deposition conditions have properties typical of device‐gradea‐Si:H. These morphology observations suggest a structural origin for some doping‐dependent properties ina‐Si:H.