A num er ical pr ocedure based on the time -depende nt K ohn { Sham equation w ith an impro ved boundar y conditio n for the mo delin g double barrier resonant tunneling dio de is presented . T he dependence of current comp onents on w ell w idths in Al GaA s/GaA s/A lGaA s structure is studied. A n oscillatory b ehavior w as observed as the w idth of the well is changed. Our evaluation show s that this oscillati on cannot attribute to the w ell-know n oscilla tion at resonance state.