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Defect states and their electric field-enhanced electron thermal emission in heavily Zr-doped β-Ga2O3 crystals
Applied Physics Letters ( IF 4 ) Pub Date : 2020-11-23 , DOI: 10.1063/5.0029442
Rujun Sun 1 , Yu Kee Ooi 1 , Arkka Bhattacharyya 1 , Muad Saleh 2 , Sriram Krishnamoorthy 1 , Kelvin G. Lynn 2 , Michael A. Scarpulla 1, 3
Affiliation  

Performing deep level transient spectroscopy (DLTS) on Schottky diodes, we investigated defect levels below the conduction band minima (Ec) in Czochralski (CZ) grown unintentionally-doped (UID) and vertical gradient freeze (VGF)-grown Zr-doped beta-Ga2O3 crystals. In UID crystals with an electron concentration of 10^17 cm-3, we observe levels at 0.18 eV and 0.46 eV in addition to the previously reported 0.86 (E2) and 1.03 eV (E3) levels. For 10^18 cm-3 Zr-doped Ga2O3, signatures at 0.30 eV (E15) and 0.71 eV (E16) are present. For the highest Zr doping of 5*10^18 cm-3, we observe only one signature at 0.59 eV. Electric field-enhanced emission rates are demonstrated via increasing the reverse bias during measurement. The 0.86 eV signature in the UID sample displays phonon-assisted tunneling enhanced thermal emission and is consistent with the widely reported E2 (FeGa) defect. The 0.71 eV (E16) signature in the lower-Zr-doped crystal also exhibits phonon-assisted tunneling emission enhancement. Taking into account that the high doping in the Zr-doped diodes also increases the electric field, we propose that the 0.59 eV signature in the highest Zr-doped sample likely corresponds to the 0.71 eV signature in lower-doped samples. Our analysis highlights the importance of testing for and reporting on field-enhanced emission especially the electric field present during DLTS and other characterization experiments on beta-Ga2O3 along with the standard emission energy, cross-section, and lambda-corrected trap density. This is important because of the intended use of beta-Ga2O3 in high-field devices and the many orders of magnitude of possible doping.

中文翻译:

重掺杂 Zr 的 β-Ga2O3 晶体中的缺陷态及其电场增强电子热发射

在肖特基二极管上执行深能级瞬态光谱 (DLTS),我们研究了在无意掺杂 (UID) 和垂直梯度冻结 (VGF) 生长的 Zr 掺杂的直拉 (CZ) 中低于导带最小值 (Ec) 的缺陷水平Ga2O3 晶体。在电子浓度为 10^17 cm-3 的 UID 晶体中,除了之前报道的 0.86 (E2) 和 1.03 eV (E3) 能级之外,我们还观察到了 0.18 eV 和 0.46 eV 的能级。对于 10^18 cm-3 Zr 掺杂的 Ga2O3,存在 0.30 eV (E15) 和 0.71 eV (E16) 处的特征。对于 5*10^18 cm-3 的最高 Zr 掺杂,我们仅在 0.59 eV 处观察到一个特征。通过在测量过程中增加反向偏压来证明电场增强的发射率。0。UID 样品中的 86 eV 特征显示声子辅助隧道效应增强的热发射,与广泛报道的 E2 (FeGa) 缺陷一致。低 Zr 掺杂晶体中的 0.71 eV (E16) 特征也表现出声子辅助隧道发射增强。考虑到 Zr 掺杂二极管中的高掺杂也会增加电场,我们建议最高 Zr 掺杂样品中的 0.59 eV 特征可能对应于较低掺杂样品中的 0.71 eV 特征。我们的分析强调了测试和报告场增强发射的重要性,尤其是在 DLTS 和其他 β-Ga2O3 表征实验期间存在的电场,以及标准发射能量、横截面和 λ 校正陷阱密度。
更新日期:2020-11-23
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