不同生长条件下ZnO薄膜电学性质的研究

Abstract

The high background electron concentration in ZnO films can compensate the forming of acceptor,which causes difficulties for p-type doping. Understanding the source of the high background electron concentration is helpful to realize high-efficient p-type doping. In this paper,a series of ZnO thin films were grown on a-plane sapphire substrates under different vacuum by molecular beam epitaxy. The samples grown under low vacuum show high carrier concentration of about1019cm- 3,however,the electron concentration of the samples grown under high vacuum is significantly lower than the samples grown under high vacuum by three orders of magnitude. For the samples grown under low vacuum,the electron density did almost not change after annealing with various post-treatment,indicating the intrinsic defects,such as oxygen vacancy,are not the main source of electrons in ZnO films. The high background electron concentration should originated from the impurities unintentionally introduced during the growth. The samples grown under low vacuum showed a strong photoluminescence peak at 3. 366 eV at 85 K,which is related to shallow-donorbound exciton. For the samples grown under high vacuum,this emission was weakened markedly.Therefore,defects related to hydrogen were assigned to the main source of the high electron concentrations in the case of low vacuum growth.