Hydrogenated amorphous and microcrystalline GaAs films prepared by radio-frequency magnetron sputtering

We report on the optical absorption, adhesion, and microstructure of radio-frequency magnetron sputtered films of hydrogenated amorphous and microcrystalline GaAs films for the 1 to 25 mum infrared wavelength range. Sputtering parameters which were varied include sputtering power, temperature and pressure, and hydrogen sputtering-gas concentration. Transmission electron microscopy results show a sharp transition from purely amorphous GaAs to a mixture of microcrystalline GaAs in an amorphous matrix at a substrate-holder temperature of 34+/-2 degreesC. By optimizing the sputtering parameters, the optical-absorption coefficient can be decreased below 100 cm(-1) for wavelengths greater than about 1.25 mum. These results represent the lowest reported values of optical absorption for sputtered films of GaAs directly measured by spectrophotometry for the near-infrared wavelength region. (C) 2002 American Institute of Physics.