Barcodes (as in: 1D) can only contain the characters specified in their specification. For example, EAN13 can only hold numbers, Code128 can contain numbers, US-ASCII letters and some special characters, etc.
If you are talking about 1D-Barcodes, look into their definition. I know of no 1D-barcode that can hold unicode (specifically arabic) letters.
QR-codes should be able to contain unicode characters. Both the application that generates the QR-code and the application that interprets the QR-code need to be able to use UTF8/16 encoding, however.
It might help to add a BOM (byte-order-mark) that indicates which type of unicode character set the content is encoded in. The interpreting application might consider this to use the proper text encoding for displaying the contents of the barcode.