Photothermal investigation for optimizing a lattice strain relaxation condition of InGaAs/GaAsP superlattice photovoltaic structures from a nonradiative transition point of view
Photothermal investigation for optimizing a lattice strain relaxation condition of InGaAs/GaAsP superlattice photovoltaic structures from a nonradiative transition point of view
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DOI：
10.1088/1361-6463/aca210
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发表时间：
2023-01-05
影响因子：
3.4
通讯作者：
Ikari, Tetsuo
中科院分区：
文献类型：
--
作者：
Fukuyama, Atsuhiko;Yamamoto, Naoki;Ikari, Tetsuo
通过选择合适的制造参数，如量子阱和势垒层的组成和厚度，优化了InGaAs/GaAsP超晶格（SL）光伏结构的载流子收集效率。然而，从光激发载流子的非辐射跃迁的角度还没有观察到深刻的见解。在这项研究中，压电光热（PPT）和光致发光（PL）测量作为温度从100到340 K的函数。利用压电传感器，PPT信号检测非辐射复合（NR）产生的热量。QW层的铟组成固定为0.3，阻挡层中的磷组成x[P]由0.4变为0.6。利用e1和hh1量子化能级光激发载流子的速率方程，分析了观测到的PPT和PL信号强度与温度的关系。考虑了电子和空穴的四种载流子耗散过程，即辐射复合、NR、QW热激发热逸（TE）和热激发后隧穿（TATE）。热活化能包括在NR、TE和TATE过程中。由于非辐射和辐射跃迁分量会产生PPT和PL信号，因此对温度行为的曲线拟合使我们能够确定活化能。然后我们发现NR过程的活化能在x[P] = 0.45处达到最大值。在TE和TATE过程中没有观察到这样的最大值。这一结果可以解释为，当x[P]增加时，整个SL结构范围内的应变值条件与QW、层间和势垒层界面处的局部残余应变之间的权衡。由于没有软件可以理论上计算NR过程的活化能，我们证明了目前PPT实验方法在研究载流子输运特性方面的实用性。
The carrier collection efficiencies of InGaAs/GaAsP superlattice (SL) photovoltaic structures were optimized by choosing adequate manufacturing parameters, such as the composition and thickness of the quantum wells (QWs) and barrier layers. However, no insights have been observed from the viewpoint of the nonradiative transition of photoexcited carriers. In this study, piezoelectric photothermal (PPT) and photoluminescence (PL) measurements were performed as a function of temperature from 100 to 340 K. Using a piezoelectric transducer, the PPT signal detected the heat generated by nonradiative recombination (NR). The indium composition of the QW layer was fixed at 0.3, and the phosphorus composition x[P] in the barrier layer was changed from 0.4 to 0.6. The observed temperature dependences of the PPT and PL signal intensities were analyzed using a rate equation for the photoexcited carriers in e1 and hh1 quantized levels. Four carrier dissipating processes, namely, radiative recombination, NR, thermal escape from the QW thermal excitation (TE), and tunneling after thermal excitation (TATE), were considered for both electrons and holes. Thermal activation energies were included in the NR, TE, and TATE processes. Because nonradiative and radiative transition components cause PPT and PL signals, curve fitting of the temperature behavior enabled us to determine the activation energies. We then found that the activation energy of the NR process reached a maximum at x[P] = 0.45. No such maxima were observed for the TE and TATE process. This result was explained by a trade-off between the strain valance condition over the entire range of the SL structure and the local residual strain at the interfaces between the QW, interlayer, and barrier layer when x[P] increased. Because no software can theoretically calculate the activation energy of the NR process, we demonstrated the usefulness of the present PPT experimental methodology for investigating carrier transport properties.