LPE生长GaN的不同极性面的光学性质

极化效应会导致GaN基发光器件的效率降低,因此关于非极性和半极性GaN单晶的研究受到了广泛关注。为了进一步探究不同极性GaN的发光特性和杂质掺入的内在机理,本文利用钠助熔剂法侧向生长出的不同极性面的GaN单晶作为研究对象,对比了不同极性面的光学性质及杂质掺入特点,讨论了黄光带(YL)峰的起源及其影响因素。首先利用阴极荧光(CL)、光致发光(PL)对液相外延(LPE)法生长的不同极性方向的GaN的光学性质进行了研究。结果表明,不同的生长极性面会显露出不同的光学特性。朝着侧向生长的 1122] 和 1120] GaN的CL和PL特性相似,但与 0001] GaN的光谱有较大差异。PL杂质峰包含两个肩峰peak 1(2.2 eV)和peak 2 (2.6 eV),在不同极性面中强度占比各不相同,推测分别与C_NO_N和C_N缺陷的0/+能级的跃迁有关。通过SIMS元素分析,C元素分布较为均匀,O元素分布存在较大差异,在1122]区域沿着生长方向O含量逐渐增加,结合PL中2.2 eV处峰的强度增加,进一步证明了2.2 eV处的峰强与O含量存在正相关性。

Optical Properties of LPE-GaN Grown in Different Polar Directions

The polarization effect in gallium nitride (GaN) will reduce the efficiency of light-emitting diodes (LEDs), so the research on non-polar and semi-polar bulk GaN has received extensive attention. The purpose of our research is to optimize the growth of bulk GaN by exploring the luminescence characteristics between different polar directions of GaN and the fundamental mechanism of impurity doping. In this paper, the bulk GaN single crystals with different polar directions grown laterally by the Na-flux method are used as the research object. The optical properties and impurity distribution characteristics of bulk GaN with different polar directions were compared, and the origin of yellow luminescence (YL) band of bulk GaN and its influencing factors were discussed. At the beginning, the optical properties of GaN bulk single crystals with different polar directions by liquid phase epitaxy (LPE) were studied by cathodoluminescence (CL) and photoluminescence (PL). The experimental results show that optical properties of bulk GaN with different growth polar directions are different. The CL and PL characteristics of 1122] and 1120] GaN grown in the lateral direction are similar, but the spectra of 0001] GaN is quite different. The impurity peak of the photoluminescence contains two shoulder peaks, peak 1 (2.2 eV) and peak 2 (2.6 eV), which accounted for different proportions in different polar directions. We speculate that they are related to the C_NO_N complex and the 0/+ energy of C_N defect respectively. Then through time of flight secondary ion mass spectrometer (TOF-SIMS) element analysis, the distribution of C impurity is relatively uniform. There is a big difference in the distribution of oxygen impurity. In the 1122] GaN region, the oxygen impurity content gradually increases along the growth direction. Combined with the increase in the intensity of the peak 1 at 2.2 eV in the PL spectra, this phenomenon further proves that there is a positive correlation between the intensity of the 2.2 eV peak and the oxygen impurity.