SIMS analysis of ZnO films co-doped with N and Ga by temperature gradient pulsed laser deposition

摘要

Composition spread ZnO:(Ga,N) films were deposited on ScAlMgO_4 substrates using both temperature gradient method and alternating pulsed laser deposition (PLD) onto two targets of highly-pure and Ga-doped ZnO. The intensity ratios of ~(14)N~(16)O~- and ~(71)Ga~(16)O~- to that of ~(70_)Zn~(16)O~- detected by secondary ion mass spectroscopy (SIMS) analysis were found to correspond to N and Ga concentrations (C_N and C_(Ga)), respectively. Incorporation of nitrogen into ZnO film with O-face (-c) polarity deposited by PLD depended strongly on substrate temperature due to thermal-activated desorption of N, while C_N into Zn-face (+c) ZnO film was independent of the temperature. The ratio of C_N/C_(Ga) in the ZnO:(Ga,N) film covered a wide range including the value of 2, satisfying the theoretical prediction to produce p-type carrier in ZnO, at various C_(Ga) levels (10~(18)-10~(20) cm~(-3)). However, p-type conduction was not observed in Hall bars array patterned on the composition spread films. The temperature gradient method and the quantitative SIMS analysis revealed that simple adjustment of C_N/C_(Ga) ratio was not able to lead to production of p-type ZnO film.