厚度对MOCVD生长InN薄膜位错特性与光电性质的影响

Thickness dependent dislocation,electrical and optical properties in InN films grown by MOCVD

研究了金属有机物化学气相沉积法制备的不同厚度InN薄膜的位错特性与光电性质.基于马赛克微晶模型,通过X射线衍射非对称面摇摆曲线测量,拟合出样品刃型位错密度分别为4.2×1010cm-2和6.3×1010cm-2,并发现样品的微晶扭转角与位错密度随薄膜厚度增加而减小.通过室温霍尔效应测量得到样品载流子浓度分别为9×1018cm-3和1.2×1018cm-3,采用氮空位作为背景载流子起源的模型解释了随厚度增加载流子浓度的减小与迁移率的增大.光致发光峰随温度的S形非单调变化表明材料中的局域态参与了光学跃迁过程,结合局域态发光和能带收缩效应计算得到样品的局域化能量分别为5.05meV和5.58meV,指出较厚样品中缺陷态的减少是载流子局域化效应削弱的原因.

InN thin films with different thicknesses are grown by metal organic chemical vapor deposition, and the dislocations, electrical and optical properties are investigated. Based on the model of mosaic crystal, by means of X-ray diffraction skew geometry scan, the edge dislocation densities of 4.2 × 10^10 cm^-2 and 6.3 × 10^10 cm^-2 are fitted, and the decrease of twist angle and dislocation density in thicker films are observed. The carrier concentrations of 9 × 10^18 cm^-3 and 1.2 × 10^18 cm^-3 are obtained by room temperature Hall effect measurement. VN is shown to be the origin of background carriers, and the dependence of concentration and mobility on film thickness is explained. By the analysis of S-shape temperature dependence of photoluminescence peak, the defects induced carrier localization is suggested be involved in the photoluminescence. Taking both the localization and energy band shrinkage effect into account, the localization energies of 5.05 meV and 5.58 meV for samples of different thicknesses are calculated, and the decrease of the cartier localization effect in the thicker sample can be attributed to the reduction of defects.