Append a character to a list n times

I want to create random data for testing. I want to fill an array with 100 strings of random length with the letter 'A'.

example:

array[0] = "AAAAA"
array[1] = "AAAAAAAA"
array[2] = "A"
...

char **create_string()
{
    char **array = malloc(sizeof(**array)); 

    srand((unsigned int)time(NULL));
    int random = 0;

    int i, j;
    for(int i=0; i<100; i++)
    {
        random = rand() % 100;
        for(j=0; j < random; j++)
        {
           array[i] = // some sort of string append that would be cheap.
        }
    }
}

I was looking at this C string append and they use strcat. Is there a better way to solve my problem? Since I will be running in a loop to create those random size strings.