Self-limiting deposition of semiconducting ZnO by pulsed plasma-enhanced chemical vapor deposition

Abstract

Self-limiting growth of zinc oxide was accomplished over a temperature range from 25to155°C by pulsed plasma-enhanced chemical vapor deposition using dimethyl zinc [Zn(CH3)2] as the metal precursor. The deposition rate was independent of plasma exposure (1–5s) but was found to increase from 1.4to6.0Å∕cycle as a function of temperature. Over the narrow range explored, substrate temperature had a dramatic impact on the film structure and properties. Amorphous films were obtained at room temperature, while a polycrystalline morphology with a preferred (100) orientation developed as the temperature increased. The electrical resistivity decreased linearly with temperature from 45to∼2Ωcm. Spectroscopic characterization showed that films deposited at room temperature were contaminated by carbon and hydroxyl impurities; however, these defects were attenuated with temperature and were not detected in films deposited above 64°C. Room temperature photoluminescence was dominated by defect emission in most films; however, this signal was attenuated, and a strong band edge emission was observed for films deposited at temperatures >135°C. Film quality was comparable to material grown by plasma-enhanced atomic layer deposition in the same reactor; however, precursor requirements and net deposition rates were improved by an order of magnitude.