The asymmetry of GaAs/A1GaAs quantum wells grown by molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) is investigated by measuring the current-voltage (I-V) and responsivity characteristics of quantum well infrared photodetectors (QWIPs). Different asymmetry behaviors were observed in MBE and MOCVD grown devices due to their different growth mechanisms. Furthermore. the role of one of the post growth techniques, ion implantation induced quantum well intermixing, on varying the asymmetry of the MBE QWIPs was also studied.