Cr/Ni/Au ohmic contacts to the moderately doped p- and n-GaN

We report new Cr/Ni/Au and Ni/Cr/Au tri-layer metallization schemes for achieving low resistance ohmic contacts to moderately doped p-(similar to 1 x 10(17)/cm(3)), and n-GaN (similar to 1 10(18)/cm(3)) respectively. The metallizations were thermally evaporated on 2 mu m-thick GaN layers grown on c-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD). Comparisons with bi-layer metallizations such as Ni/Au and CriAu were also made. The Cr/Ni/Au contacts showed a low specific contact resistivity of 9.1 x 10(-5) Omega . 2 cm(2) to n-GaN while that of Ni/Cr/Au to p-GaN was 8.3 x 10(-2) Omega . cm(2). The Ni/Cr/Au contacts also showed a low specific contact resistivity of 2.6 x 10(-4) Omega . cm(2) to n-GaN. The Ni/Cr/Au metallization could made reasonable ohmic contacts to p- and n-GaN simultaneously.