Adding a prime symbol to greek letter in ggplot2

I want to aotate a ggplot2 graph with lambda' or in LaTex speak $lambda^{prime}$, but this will not parse in R

parse(text='lambda"'"')
Error in parse(text = "lambda"'"") : 
  <text>:1:7: unexpected string constant
1: lambda"'"

Does anybody know how to do this? I think this is why ggplot throws an error to

aotate('text',x=x,y=y,label='lambda"'"',parse=TRUE)