Yes, to use C# 6 features, you need a C# 6 compiler. Visual Studio 2013 doesn’t have a C# 6 compiler. Visual Studio 2015 does.
There have been Roslyn pre-releases for Visual Studio 2013, but they don’t implement the final C# 6: they actually don’t implement all the features, and what they do implement is different from the final C# 6 behaviour.