Photoluminescence of Er3+-implanted amorphous hydrogenated silicon suboxides
Photoluminescence of Er3+-implanted amorphous hydrogenated silicon suboxides
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Er3 注入的非晶氢化硅低氧化物的光致发光
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发表时间：
2003
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通讯作者：
C. Buchal
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作者：
A. Janotta;M. Schmidt;R. Janssen;M. Stutzmann;C. Buchal
铒离子掺入到非晶氢化硅亚氧化物$(aensuremath{-}{mathm {SiO}}_{x}: mathm {H})$中，克服了${mathm {Er}}^{3+}$在$censuremath{-} mathm {Si}$中溶解度有限、室温下强猝灭、需要与电负性原子共掺杂等缺点。$aensuremath{-}{mathrm{SiO}}_{x}:mathrm{H}$合金具有增强的Er溶解度和易于变化的氧含量，从而为有效的Er发光提供了有利的原子环境，并且由于更深的局域带尾态而减少了激发背转移。在本研究中，将${mathm {Er}}^{3+}$剂量注入氧含量在0到44 at之间的-${mathm {SiO}}_{x}: mathm {H}$中，剂量高达$7ifmmode imeselse exttimesfi{}{10}^{14}{mathm {cm}}^{ensuremath{-}2}$。%。研究了${mathm {Er}}^{3+}$离子和${mathm {SiO}}_{x}$基体的吸收系数和光致发光（PL）光谱等光学性质与铒注入剂量、氧含量、缺陷密度、温度和退火处理的关系。发现退火是激活1.54 μ m的特征Er PL的必要条件，这主要是由于减少了注入引起的缺陷。通过电子自旋共振或亚间隙吸收测量，发现本征${mathm {SiO}}_{x}$和Er PL的强度与缺陷密度成反比。在退火过程中，铒离子的PL进一步增强，这可能是由于铒离子的结构排列更好的结果。Er PL强度随注入剂量近似线性增加。增加$aensuremath{-}{mathrm{SiO}}_{x}:mathrm{H}$的氧含量（以及相应的光学带隙）不会引起铒发光能量和强度的剧烈变化，而随着带隙的增大，本征PL会向更高的光子能量转移。几个百分点的低氧浓度提供了有利的Er环境。$aensuremath{-}{mathrm{SiO}}_{x}:mathrm{H}$作为宿主矩阵的主要优点是通过温度相关的PL测量揭示的。对于高氧含量，${mathm {Er}}^{3+}$和本然PL的热猝灭被强烈地减弱。在$aensuremath{-}{mathm {SiO}}_{x}$ sample中包含44 at。在77 ~ 300k之间，Er PL只淬灭了20%。相比之下，所有[O]的内在PL的猝灭大约比Er PL的猝灭强一个数量级。这些PL测量得到了宽光谱范围内PL激发实验的补充。我们已经观察到，与带对带激发相比，用亚带隙光泵浦${mathm {Er}}^{3+}$ PL的激发效率提高了一个数量级。讨论了目前提出的两种${mathm {Er}}^{3+}$激励模型、缺陷相关的俄格效应和F"orster传递机制的实验结果。
Erbium ions incorporated into amorphous hydrogenated silicon suboxides $(aensuremath{-}{mathrm{SiO}}_{x}:mathrm{H})$ allow to overcome the disadvantages of ${mathrm{Er}}^{3+}$ in $censuremath{-}mathrm{Si}$ such as the limited solubility, the strong quenching of the luminescence at room temperature, and the need for co-doping with electronegative atoms. $aensuremath{-}{mathrm{SiO}}_{x}:mathrm{H}$ alloys have an enhanced Er solubility and easily variable oxygen content, thereby providing favorable atomic environments for an efficient Er luminescence and reduced excitation backtransfer due to deeper localized band-tail states. In the present study, ${mathrm{Er}}^{3+}$ doses up to $7ifmmode imeselse exttimesfi{}{10}^{14}{mathrm{cm}}^{ensuremath{-}2}$ were implanted into a-${mathrm{SiO}}_{x}:mathrm{H}$ with oxygen content between 0 and 44 at. %. Optical properties such as the absorption coefficients and the photoluminescence (PL) spectra of the ${mathrm{Er}}^{3+}$ ions and of the ${mathrm{SiO}}_{x}$ host were investigated as a function of erbium implantation dose, oxygen content, defect density, temperature, and annealing treatment. It was found that annealing is a requirement for activating the characteristic Er PL at 1.54 ensuremath{mu}m mainly due to a reduction of implantation induced defects. The intensity of both the intrinsic ${mathrm{SiO}}_{x}$ and the Er PL was found to be inversely proportional to the defect density as measured by electron spin resonance or subgap absorption. The Er PL is additionally enhanced upon annealing, probably as a result of better structural arrangements of the Er ions. The Er PL intensity increases approximately linearly with the implantation dose. An increase of the oxygen content (and correspondingly of the optical band gap) of $aensuremath{-}{mathrm{SiO}}_{x}:mathrm{H}$ causes no drastic changes in the erbium luminescence energy and intensity, whereas the intrinsic PL shifts to higher photon energies according to the larger band gap. Already low O concentrations of a few percent provide favorable Er environments. The main advantage of $aensuremath{-}{mathrm{SiO}}_{x}:mathrm{H}$ as a host matrix is revealed by temperature-dependent PL measurements. For high oxygen contents, the thermal quenching of both the ${mathrm{Er}}^{3+}$ and the intrinsic PL is strongly reduced. In an $aensuremath{-}{mathrm{SiO}}_{x}$ sample with 44 at. % oxygen, the Er PL is only quenched by 20% between 77 and 300 K. In contrast, the quenching of the intrinsic PL for all [O] is roughly one order of magnitude stronger than that of the Er PL. These PL measurements were complemented by PL excitation experiments over a wide spectral range. We have observed that the ${mathrm{Er}}^{3+}$ PL is excited about one order of magnitude more efficiently when pumped with sub-band-gap light compared to band-to-band excitation. The experimental results are discussed with regard to the two currently proposed ${mathrm{Er}}^{3+}$ excitation models, the defect-related Auger effect and the F"orster transfer mechanism.