Diamond-like carbon thin films as antireflective and protective coatings of GaAs elements and devices

Diamond-like carbon (DLC) films were deposited directly on GaAs substrates by a capacitively coupled 13.56 MHz glow discharge in a CH4 plasma. The dep osition process for antireflective DLC coating deposition on GaAs was optim ized. DLC films of different thicknesses were deposited to investigate IR s pectral characteristics. DLC films on GaAs increased microhardness from 500 kg/mm(2) for the uncoated substrate to 1200 kg/mm(2). The spectral transmi ttance of the bare and coated substrates in the 2.5<lambda<16.5 mu m region was measured. DLC layer thickness affects the optical transmittance of the coated substrate. The peak transmittance with DLC coatings on both sides o f the substrate reaches 95%, with about 1% absorption and 4% reflection. (C ) 2000 Society of Photo-Optical instrumentation Engineers. [S0091-3286(00)0 0504-3].