Experimental results on the dependence of the Au&sngbnd;GaAs barrier height on the thicknessdof the oxide film reported by Pruniaux and Adams indicate that &PHgr;B=&PHgr;i+Ad. This communication shows that neglecting the effect of surface states in the Cowley‐Sze model predicts a linear decrease of barrier height with increasing oxide thickness. The observed increase of barrier height with increasing oxide thickness may be partly due to surface states at the oxide‐semiconductor interface. A model that includes the effects of surface states and of screening on the metal side is proposed to explain the various values for &PHgr;i.