▁, ▁ ▁being ▁the ▁F erm i ▁level . ▁The ▁P SD ▁ ▁of ▁the ▁fl uct u ation ▁ ▁due ▁to ▁a ▁single ▁trap ▁then ▁becomes ▁, ▁where ▁ ▁is ▁the ▁Lor ent z ian ▁P SD ▁of ▁the ▁random ▁te legraph ▁signal ▁ ▁and ▁ ▁is ▁the ▁trap ▁relax ation ▁time . ▁Therefore , ▁for ▁a ▁density ▁ ▁of ▁equal ▁and ▁un cor related ▁defect s ▁we ▁have ▁a ▁total ▁P SD ▁ ▁of ▁the ▁g - r ▁noise ▁given ▁by ▁▁ ▁. ▁ ▁F lick er ▁noise ▁ ▁When ▁the ▁defect s ▁are ▁not ▁equal , ▁for ▁any ▁distribution ▁of ▁ ▁( except ▁a ▁sharp ly ▁pe aked ▁one , ▁as ▁in ▁the ▁above ▁case ▁of ▁g - r ▁noise ), ▁and ▁even ▁for ▁a ▁very ▁small ▁number ▁of ▁tra ps ▁with ▁large ▁, ▁ ▁the ▁total ▁P SD ▁ ▁of ▁i , ▁corresponding ▁to ▁the ▁sum ▁of ▁the ▁P SD ▁ ▁of ▁all ▁the ▁ ▁( stat ist ically ▁independent ) ▁tra ps ▁of ▁the ▁device , ▁becomes ▁▁ ▁, ▁ ▁where ▁ ▁down ▁to ▁the ▁frequency ▁, ▁ ▁being ▁the ▁largest ▁ ▁and ▁ ▁a ▁proper ▁coefficient . ▁In ▁particular , ▁for ▁un ip olar ▁conduct ing ▁materials ▁( e . g ., ▁for ▁electrons ▁as ▁carri ers ) ▁it ▁can ▁be ▁ ▁and , ▁for ▁trap ▁energy ▁levels ▁, ▁from ▁ ▁we ▁also ▁have ▁, ▁so ▁that ▁from ▁the ▁above ▁equation ▁we ▁obtain , ▁▁ ▁, ▁ ▁where ▁ ▁is ▁the ▁total ▁number ▁of ▁the ▁carri ers