How to generate all possible combinations and randomize [closed]

I want to generate a matrix with all possible non-repeating combinations & then randomize their distribution.

Example: Data Set: {A,B, C, D} String Length=4 (4^4=256 combinations)

So a 16 x 16 matrix would be generated & scrambled.

AAAA AAAB AAAC... etc. would be randomly distributed within the matrix without AAAA or any other combination being repeated.

Any ideas are greatly appreciated! Thanks!