Mechanism and performance of forward and reverse bias electroluminescence at 1.54 mu m from Er-doped Si diodes
Mechanism and performance of forward and reverse bias electroluminescence at 1.54 mu m from Er-doped Si diodes
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DOI：
10.1063/1.363935
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发表时间：
1997-03-15
影响因子：
3.2
通讯作者：
Spinella, C
中科院分区：
文献类型：
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作者：
Franzo, G;Coffa, S;Spinella, C
分析了掺Er单晶硅产生1.54微米电致发光的机理和效率。通过多个Er和O离子注入实现了0.25微米深的p(+)-n(+)结的光学掺杂，在0.2~0.9微米范围内实现了10(19)Er/cm(3)和10(20)O/cm(3)的均匀掺杂。结果表明，在相同的电流密度下，二极管击穿时反向偏压下的室温电致发光信号是正向偏置下的2-10倍。对谱线形状、温度和电流密度的依赖关系以及正向和反向偏置下的调制性能的详细分析使我们能够阐明造成这种差异的原因。在正向偏压下，尽管有很大的有效激发截面(在300K时为>；6×10-(17)cm(2))，但室温电致发光的效率受到Er离子的非辐射去激发过程的效率的限制(类似于总Er浓度的1%)。此外，由于在正向偏压下，Er离子在硅禁带中的Er相关能级上被电子-空穴复合激发，在二极管处理后残留的缺陷处，竞争载流子复合也降低了电致发光产额。另一方面，在反向偏压下，Er离子在薄的(约70 nm)耗尽层中被热载流子碰撞激发。在这种情况下，耗尽区的所有Er原子都是可激发的，非辐射去激发过程，如俄歇去激发自由电子，被抑制。这使得在300K时可以获得1.5×10(-4)的内部量子效率，并且可以实现二极管的快速调制。在二极管关断时，激发的Er离子被嵌入二极管的重掺杂(类似于10(19)/cm(3))中性区域，在那里俄歇类型的去激发过程产生Er离子的快速衰减，从而实现高于80 kHz的调制频率。在反向偏压下实现更高效率的主要限制是较薄的可激发区和具有足够能量撞击激发Er离子的有限部分热载流子。(C)1997年美国物理研究所。
We have analyzed the mechanisms and the efficiency of the 1.54 mu m electroluminescence from Er-doped crystalline Si. Optical doping of a 0.25 mu m deep p(+)-n(+) junction was achieved by multiple Er and O implants which realize a uniform concentration of 10(19) Er/cm(3) and 10(20) O/cm(3) from 0.2 to 0.9 mu m from the surface. It has been found that, for the same current density passing through the device, the room temperature electroluminescence signal is 2-10 times higher under reverse bias at the diode breakdown than under forward bias. Detailed analyses of the spectrum line shape, temperature, and current density dependencies and modulation performances under both forward and reverse bias allowed us to elucidate the reasons for this difference. In forward bias, in spite of the large effective excitation cross section (>6 X 10-(17) cm(2) at 300 K), the efficiency of room temperature electroluminescence is limited by the small number of excitable sites (similar to 1% of the total Er concentration) and by the efficiency of nonradiative de-excitation processes of the Er ions. Furthermore, since in forward bias Er ions are excited by electron-hole recombination at an Er related level in the Si band gap, the electroluminescence yield is also reduced by competitive carrier recombinations at the residual defects left over after diode processing. On the other hand, under reverse bias, Er ions are excited by hot carrier impact excitation in the thin (similar to 70 nm) depletion layer. In this case all of the Er atoms in the depletion region are excitable and nonradiative de-excitation processes, such as Auger de-excitation to free electrons, are inhibited. This allows one to achieve an internal quantum efficiency of 1.5 X 10(-4) at 300 K. Moreover, fast modulation of the diode can be achieved. At the diode turn-off, the excited Er ions are embedded in the heavily doped (similar to 10(19)/cm(3)) neutral regions of the diode where Auger-type de-excitation processes produce fast decay of the Er ions thus allowing to achieve modulation frequencies higher than 80 kHz. The major limitations to the achievement of a higher efficiency under reverse bias are the thin excitable region and the Limited fraction of hot carriers having enough energy to impact excite the Er ions. (C) 1997 American Institute of Physics.