Transposed convolution as umpsampling in DCGAN
This checkerboard effect arises due to taking sum of the overlapping regions during the transpose-convolution operation. Post convolution, in the output, the overlapping pixels have a higher magnitude than the surrounding pixels.
Try using a filter size of 4x4 along with a stride 2 transpose convolution. It may help to alleviate this problem.

For more information, watch this lecture from 30th minute.