Thermal pretreatment of sapphire substrates prior to ZnO buffer layer growth

Shimin Huang, Shulin Gu, Shunming Zhu, Ran Gu, Kun Tang, Jiandong Ye, Rong Zhang, Yi Shi, Youdou Zheng

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

The properties of ZnO buffer layers grown via metal-organic chemical vapor deposition (MOCVD) on sapphire substrates after various thermal pretreatments are systematically investigated. High-temperature pretreatments lead to significant modifications of the sapphire surface, which result in enhanced growth nucleation and a consequent improvement of the surface morphology and quality of the ZnO layers. The evolution of the surface morphology as seen by atomic force microscopy indicates an obvious growth mode transition from three-dimensional to quasi-two-dimensional as the pretreatment temperature increases. A minimum surface roughness is obtained when the pretreatment temperature reaches 1150 °C, implying that a high-temperature pretreatment at 1150 °C or above may lead to a conversion of the surface polarity from O-face to Zn-face, similar to processes in GaN material growth via MOCVD. By analyzing the evolution of the film properties as a function of pretreatment temperature, the optimal condition has been determined to be at 1150 °C. This study indicates that a high-temperature pretreatment is crucial to grow high-quality ZnO on sapphire substrates by MOCVD.

Original languageEnglish
Article number051203
JournalJournal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures
Volume31
Issue number5
DOIs
Publication statusPublished - Sept 2013
Externally publishedYes

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