ins ulating ▁cry st als ▁In ▁the ▁presence ▁of ▁excess ▁ar sen ic , ▁Ga As ▁bou les ▁grow ▁with ▁cry stal log raph ic ▁defect s ; ▁specifically , ▁ar sen ic ▁ant is ite ▁defect s ▁( an ▁ar sen ic ▁atom ▁at ▁a ▁gal li um ▁atom ▁site ▁within ▁the ▁cry stal ▁lattice ). ▁The ▁electronic ▁properties ▁of ▁these ▁defect s ▁( inter act ing ▁with ▁others ) ▁cause ▁the ▁F erm i ▁level ▁to ▁be ▁p inned ▁to ▁near ▁the ▁center ▁of ▁the ▁band ▁gap , ▁so ▁that ▁this ▁Ga As ▁cry stal ▁has ▁very ▁low ▁concentration ▁of ▁electrons ▁and ▁holes . ▁This ▁low ▁car rier ▁concentration ▁is ▁similar ▁to ▁an ▁intr insic ▁( per fect ly ▁und oped ) ▁cry stal , ▁but ▁much ▁easier ▁to ▁achieve ▁in ▁practice . ▁These ▁cry st als ▁are ▁called ▁" sem i - ins ulating ", ▁reflect ing ▁their ▁high ▁resist ivity ▁of ▁ 1 0 7 – 1 0 9 ▁ Ω · cm ▁( which ▁is ▁quite ▁high ▁for ▁a ▁sem icon duct or , ▁but ▁still ▁much ▁lower ▁than ▁a ▁true ▁ins ulator ▁like ▁glass ). ▁ ▁Et ch ing ▁W et ▁et ch ing ▁of ▁Ga As ▁industri ally ▁uses ▁an ▁ox id izing ▁agent ▁such ▁as ▁hydro gen ▁per ox ide ▁or ▁b rom ine ▁water , ▁and ▁the ▁same ▁strategy ▁has ▁been ▁described ▁in ▁a ▁pat ent ▁rel ating ▁to ▁processing ▁sc rap ▁components ▁containing ▁Ga As ▁where ▁the ▁ ▁is ▁complex ed ▁with ▁a