MOCVD生长中载气H_2对N掺杂ZnO性质的影响

The Effect of Carrier Gas H_2 Used during MOCVD-growth on the Properties of N-doped ZnO

采用MOCVD方法在石英衬底上生长ZnO。实验使用二乙基锌(DEZn)为锌源,N2O作为氧和氮源,H2作为载气。采用PL和Raman光谱方法对ZnO样品进行表征,结果表明H2的加入大幅度减少薄膜中碳的掺入,明显改善了薄膜的光学质量。采用N2O离化技术,可以进一步提高其带边峰的强度,抑制带内发光。XRD测量表明,生长的ZnO薄膜具有c轴择优取向。目前生长高质量N掺杂的p型ZnO薄膜是很困难的,而H2作为载气的加入明显改善了ZnO薄膜的光学性质,在生长过程中加入H2将为获得高质量N掺杂的p型ZnO薄膜提供一种途径。

As a versatile wide band gap semiconductor material, ZnO has a variety of applications including gas sensors, piezoelectric devices, field effect transistors, solar cells, and so on. Particularly, the application of ZnO in blue and ultraviolet light emitting diodes （LED） and laser diodes （LD） have attracted much attention in the past ten years, because it has the wide-bandgap of 3.37 eV at room temperature （RT） and the large exciton binding energy of 60 meV. Many growth techniques for single-crystalline ZnO films have been used, such as molecular beam epitaxy （MBE）, metal-organic chemical vapour deposition （MOCVD） , RF magnetron sputtering, and pulsed laser deposition （PLD）. Among these techniques, MOCVD has many advantages for the semiconductors production and has been used to manufacture many semiconductor devices. MOCVD growth of ZnO requires appropriate zinc and oxygen precursor. For the group 11 element, the mostly used zinc precursor is a metal-organic compounds like diethyl （DEZn） and dimethyl （DMZn）. For the group VI precursor, a large number of oxygen-containing compounds was widely used： gases like 02, CO2, NO, N2O;water and several types of organic compounds like alcohols, aldehydes, ketons. During the growth of ZnO, kinds of carrier gas were used to introduce zinc and oxygen precursor into growth chamber. Because of the huge volume of the carrier gas and the likely reaction with zinc precursor or oxygen precursor, it has the obvious influence on the quality of ZnO. In this experiment, argon（ Ar）, nitrogen （N2）and hydrogen （H2） were used to compare their effect on the growth of ZnO; DMZn were used as the zinc precursor and N2O as oxygen precursor. ZnO films were grown on quartz substrate by LP-MOCVD. Crystalline quality, and Optical properties were studied with photoluminescence, X-ray diffraction （XRD） using Cu Kct （λ=0.154 056 nm）, Raman spectra. The growth rate of ZnO was measured with the step profiler. Compared to Ar, the optical properties were improved by using H2 as the cartier gas of N2O. The quantity of unintended doped carbon was decreased. Ionization strengthened the ultraviolet emission and weakened the visible emission of ZnO films. According to the measure of XRD, the ZnO films had （0002） preferred orientation.