退火气氛对p-GaN材料及其欧姆接触性能的影响

Effect of Annealing Ambient on p-GaN Material and Its Ohmic Contact Characteristics

利用金属有机化学气相沉积（MOCVD）制备了Mg掺杂的p-GaN外延材料,并在不同气氛下对其进行退火,系统研究了不同退火气氛对p-GaN材料性质及欧姆接触性能的影响。利用X射线衍射（XRD）、光致发光（PL）谱和原子力显微镜（AFM）对样品进行测试和表征。结果表明,不同气氛退火均能降低p-GaN材料的XRD半高宽,改善其晶体质量,并提高其迁移率;此外,相较于纯N2和纯O2,空气气氛退火的p-GaN材料的空穴浓度最高,欧姆接触性能最优,其比接触电阻率可低至4.49×10（-4）Ω·cm^2。分析认为：空气气氛退火减少了p-GaN中的氮空位,降低了自补偿效应;空气中的O2与H结合,抑制了H的钝化效应,提高了Mg的激活率,进而改善了p-GaN材料的欧姆接触特性。

Mg-doped p-GaN epitaxy materials were prepared by metal organic chemical vapor deposition（ MOCVD） and annealed in various ambients. The effects of various annealing ambients on the material properties and ohmic contact characteristics of p-GaN materials were studied systemically. The samples were tested and characterized by X-ray diffraction（ XRD）,photoluminescence（ PL） spectra and atomic force microscope（ AFM）. The results indicate that various annealing ambients can decrease the XRD full width at half maximum,improve the crystal quality and increase the mobility of the p-GaN material. Moreover,compared with annealing in pure N2 and pure O2,the p-GaN material annealed in air ambient exhibits the highest hole concentration and best ohmic contact characteristics with a specific contact resistivity of 4. 49 × 10（-4）Ω · cm^2. Analysis suggests that the self-compensating effect is lowered through reducing the nitride vacancies at annealing in air and the activation efficiency of Mg is enhanced through inhibiting the passivation effect of H resulted from the combination of O2 and H in air. Thus,ohmic contact characteristics of the p-GaN materials were improved.