Applied Surface Science, Vol.223, No.1-3, 206-209, 2004
SIMS analysis of ZnO films co-doped with N and Ga by temperature gradient pulsed laser deposition
Composition spread ZnO:(Ga,N) films were deposited on ScAlMgO4 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 O-16(-) and (71) Ga O-16(-) 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. (C) 2003 Elsevier B.V. All rights reserved.
Keywords:ZnO :(Ga,N);polarity;composition spread;temperature gradient method;pulsed laser deposition;secondary ion mass spectroscopy