Okay, I found an app myself. It is called "Vibrance HDR". It is free ( with ad ) and it does a reasonably good job although not as pro as the paid desktop software like Aurora HDR. Just sharing here in case someone interested and chance into this thread in the future.
BTW, bracketing means combining three ( or more ) shots into one High Dynamic Range (HDR) shot. The three shots are usually set at Exposure Value : EV0, EV-2, EV+2.