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

Abstract

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.