How to make a contour plot without a square mesh?

My end goal is to plot a color-filled contour plot of my data. The closest I have been is to generate a surf with shader = interp (which is not exactly what I wanted, but is actually good enough). My figure so far looks like:

The problem is that I had to fill all the region I dont want to plot with zeros. This also causes the problem that it creates a fake yellow halo around the edge because it interpolates between the actual value I have and the 0 I had to put next to it.

The data I am using is complete data.

My code so far is:

documentclass[11pt]{article}
usepackage[top=2.54cm, bottom=2.54cm, left=2.75cm, right=2.75cm]{geometry}
usepackage{float}
usepackage{subcaption}
usepackage{pgfplots}
usepackage{amsmath}

begin{document} 
    begin{figure}[H]
        begin{tikzpicture}
        begin{axis}
        [
        width=0.335paperwidth,
        xlabel = Volts,
        ylabel = Time,
        view={0}{90},
        only marks,
        colorbar,
        colorbar style ={width = 6}
        ]
        addplot3 [surf,shader=interp] table[x index =0,y index=1,z index=2]{Ekicks.txt};
        end{axis}
        end{tikzpicture}
    end{figure}
end{document}

The original data I want to plot, without all those zeros I dont need is clean data.

EDIT

Just to be clear, the problem is not that I had to fill the empty space with zeros, I am OK with that. The actual problem is the yellow halo that is generated around the edge, which is due to my zeros instead of the actual data.

EDIT 2

So I have been able to make some progress, and I have found a way to generate a filled contour plot using pgfplots. My new result looks like this, which is almost exactly what I want:

begin{tikzpicture}
        begin{axis}
        [
        width=0.335paperwidth,
        xlabel = Volts,
        ylabel = Time,
        view={0}{90},
        only marks,
        colorbar,
        colorbar style ={width = 6}
        ]
        addplot3[contour filled={number=40}]
        table[x index =0,y index=1,z index=2]{Ekicks.txt};
        end{axis}
        end{tikzpicture}

My problem is that I still need to have a complete mesh. Does anybody know how I could just plot the values I need? Or how can I work around this, something like force all 0 to white, while all the other colors remain the same?

documentclass{article}

usepackage{pgfplots}

begin{document}

begin{tikzpicture}
begin{axis}[
  width=.7linewidth,
  xlabel={Potential in Volt},
  ylabel={Time},
  view={0}{90},
  colorbar,
  unbounded coords=jump
] addplot3 [
  surf,
  shader=interp,
] table [
  x index=0,
  y index=1,
  z index=2,
]{plot.dat};
end{axis}
end{tikzpicture}

end{document}