Passivation Mechanism of Nitrogen in ZnO under Different Oxygen Ambience

Xingyou Chen,Yunyan Zhang,Bin Yao,Qian Gong,Binghui Li,Zhenzhong Zhang

doi:10.3390/cryst9040204

Abstract

Nitrogen-doped ZnO thin films were grown on a-plane Al2O3 by plasma-assisted molecular beam epitaxy. Hall-effect measurements indicated that the nitrogen-doped ZnO films showed p-type behavior first, then n-type, with the growth conditions changing from oxygen-radical-rich to oxygen-radical-deficient ambience, accompanied with the increase of the N/O ratio in the plasmas. The increasing green emission in the low temperature photoluminescence spectra, related to single ionized oxygen vacancy in ZnO, was ascribed to the decrease of active oxygen atoms in the precursor plasmas. CN complex, a donor defect with low formation energy, was demonstrated to be easily introduced into ZnO under O-radical-deficient ambience, which compensated the nitrogen-related acceptor, along with the oxygen vacancy.

Highlights

In recent years, zinc oxide (ZnO), a wide-band-gap semiconductor material, with an exciton binding energy of 60 meV, has attracted extensive interest, due to its potential applications in ultraviolet (UV) light-emitting, lasing and photodetecting devices. [1,2,3,4] stable p-type ZnO with high hole concentrations, was difficult to be achieved, which blocks the brilliant foregrounds above
The ZnO:N thin films were grown on a-plane sapphire, by using a VG V80H plasma-assisted molecular beam epitaxy (P-MBE) system
The Radio frequency (RF) power was fixed at Structures of the samples were characterized by x-ray diffraction (XRD) with α radiation

Summary

Introduction

Zinc oxide (ZnO), a wide-band-gap semiconductor material, with an exciton binding energy of 60 meV, has attracted extensive interest, due to its potential applications in ultraviolet (UV) light-emitting, lasing and photodetecting devices. [1,2,3,4] stable p-type ZnO with high hole concentrations, was difficult to be achieved, which blocks the brilliant foregrounds above. The high background electron concentration makes p-type doping reasonably difficult. Some intrinsic donors, such as interstitial Zinc (Zni ) and oxygen vacancy (VO ), are formed, especially under zinc-rich (i.e. oxygen-deficient) ambience. P-type doping by using group V dopants needs such a zinc-rich ambience, because of the weaker electronegativity of group V elements than of oxygen. Under this circumstance, the p-type behavior would be weakened by these defects and become difficult to use. The growth ambience effects on passivation of N-related acceptor and conductivities of ZnO were studied. CN complex on oxygen site, an important shallow donor, was discussed

Experimental

Results and Discussion

Conclusions