Tunneling through a barrier

Clear[a, V0]
{a, 
        V0} = {a, V0}
Clear[A, B, R, T, z1, 
      z2]
equations = {
1 + R == 
          A + B, 
I*
            k*(1 - R) == -kappa*(A - 
                B), 
A/z2 + B*z2 == 
          T*z1, 
-kappa (A/z2 - B*z2) == 
          I*k*T*z1}
solutions = 
      Solve[equations, {A, B, R, T}]

Clear[Tout, Tamp, Tnum, 
        Tden]
Tout = (T  /.  
            solutions)[[1]]
Tnum = 
      Numerator[Tout]/(z1*2*I*z2)
Tden = 
      Denominator[Tout]/(z1*2*I*z2) // 
        Simplify
Tden = 
      Tden  /.  {z2^2 - 1 -> z2*2*sh, 
          z2^2 + 1 -> z2*2*ch}
Tden = 
      ComplexExpand[Tden]
Print["Tnum= ", 
      Tnum]
Print["Tden= ", Tden]

Clear[nn, dd, 
        Ptrans]
nn = 
      Tnum  /.  z1 -> 1
nn2 = 
      ComplexExpand[nn*Conjugate[nn]] // 
        Simplify
dd = 
      Tden
dd2 = 
      ComplexExpand[dd*Conjugate[dd]] // 
        Simplify
Ptrans[k1_, kap1_] := 
        nn2/dd2   /. {k -> k1, kappa -> kap1, 
            ch -> Cosh[kap1*a], 
sh -> 
              Sinh[kap1*a]};
Ptrans[k, 
      kappa]

{a, V0} = {5, 
          1}
Plot[
      Ptrans[Sqrt[En], Sqrt[V0 - En]], 
{En, 0, 10}, 
      PlotRange -> {{0, 10}, {0, 1}}]
Remove[
      LogPlot]
<< 
      Graphics`Graphics`
LogPlot[
      Ptrans[Sqrt[En], Sqrt[V0 - En]], 
{En, 0, 10}, 
      PlotRange -> {{0, 10}, {10^-3, 1}}]