ajax sent html input file content jquery

Question

I have a form with a file input.

<input id="frm-documentForm-documentForm-files" class="required_1" type="file" data-nette-rules="[{"op":":filled","msg":"FILE\/S are mandatory!"}]" required="" multiple="" name="files[]">

And jquery code

$('#frm-documentForm-documentForm-files').change(function() {
        $.ajax({
            url: "?do=getProperties",
            type: 'POST',
            data: this,
            processData: false,
            contentType: "multipart/form-data",
            success: function(data) {
                alert("success");
            }
        });

And when I dump post or files, both are empty. (array())

What do I need to do to fix it?

Thanks for you help.