Excimer-laser annealed ohmic contacts to n-GaAs substrates through an ultrathin reacted layer

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Abstract
An excimer laser has been employed to form ohmic contacts to n‐GaAs substrates through an ultrathin reacted layer. An eutectic AuGe alloy, Ni/AuGe (/n‐GaAs), and AuGe/Ni (/n‐GaAs) were used as ohmic metals. The lowest specific contact resistance ρc measured using the transmission line method was 6.2×10−7 Ω cm2, 2×10−6 Ω cm2, and 1.5×10−6 Ω cm2 for AuGe, Ni/AuGe and AuGe/Ni, respectively. Good surface morphology was also obtained. Depth profiles of the contacts analyzed by an Auger electron microscope show that the thickness of the transition region between the ohmic metal and GaAs was about 100 Å for AuGe and Ni/AuGe, and 300–400 Å for AuGe/Ni.