Control of p- and n-type conductivity in sputter deposition of undoped ZnO

Abstract

Recent theoretical studies have concluded that the low formation enthalpies of intrinsic donor defects should preclude achievement of p-type conductivity in undoped ZnO grown in thermal equilibrium with a molecular oxygen reservoir. This letter demonstrates that reactive sputtering can produce intrinsic p-type ZnO, controlled by adjusting the oxygen partial pressure in the sputtering plasma. We report the properties of p–n homojunctions fabricated in this way, and characterize transport in the films by Hall measurements. Our finding of p-type conductivity in undoped ZnO grown with dissociated oxygen is qualitatively consistent with the effect of higher chemical potential of atomic oxygen reactant on defect formation enthalpies. This parallels to some degree the recent attention to nitrogen acceptor incorporation by means of dissociating nitrogen source gases.