GaN二极管中通过激子Franz-Keldysh光电流光谱的局域电场测量
Local Electric Field Measurement in GaN Diodes by exciton Franz-Keldysh Photocurrent Spectroscopy
AI总结：
本文利用激子Franz-Keldysh光电流光谱，通过单一拟合参数定量测量GaN二极管局域电场，验证了其作为宽禁带器件电场探针的可行性，精度达±0.31 V。
摘要：
在GaN p-n结二极管中，通过光电流响应度数据的光谱变化观察到了激子Franz-Keldysh（XFK）效应，该效应随反向偏压的增加而红移并展宽。在较宽的光子能量范围内，光电流光谱仅使用一个决定线形的单一拟合参数，即局域偏压（$V_{l}$），即可定量拟合到XFK模型，从而唯一确定局域电场最大值和耗尽层宽度。正如预期，光谱确定的$V_{l}$值随外加偏压（$V$）线性变化，并揭示了由于静电不均匀性导致的局域电场大幅降低。通过外推$V=0$时的$V_{l}$估计了内建偏压（$V_{bi}$），与独立的C-V测量相比，表明$V_{l}$的整体精度为±0.31 V。这证明了亚带隙光电流光谱可作为宽禁带二极管中电场的局域探针，可用于绘制器件击穿区域（热点）的分布图，以改进高压器件的静电设计。
英文摘要：
The eXciton Franz-Keldysh (XFK) effect is observed in GaN p-n junction diodes via the spectral variation of photocurrent responsivity data that redshift and broaden with increasing reverse bias. Photocurrent spectra are quantitatively fit over a broad photon energy range to an XFK model using only a single fit parameter that determines the lineshape, the local bias ($V_{l}$), uniquely determining the local electric field maximum and depletion widths. As expected, the spectrally determined values of $V_{l}$ vary linearly with the applied bias ($V$) and reveal a large reduction in the local electric field due to electrostatic non-uniformity. The built-in bias ($V_{bi}$) is estimated by extrapolating $V_{l}$ at $V=0$, which compared with independent C-V measurements indicates an overall $\pm$0.31 V accuracy of $V_{l}$. This demonstrates sub-bandgap photocurrent spectroscopy as a local probe of electric field in wide bandgap diodes that can be used to map out regions of device breakdown (hot spots) for improving electrostatic design of high voltage devices.
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