Influence of AlGaN deep level defects on AlGaN/GaN 2-DEG carrier confinement
Influence of AlGaN deep level defects on AlGaN/GaN 2-DEG carrier confinement
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AlGaN深能级缺陷对AlGaN/GaN 2-DEG载流子限制的影响
DOI：
10.1109/16.906428
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发表时间：
2001
影响因子：
3.1
通讯作者：
L. Eastman
中科院分区：
文献类型：
--
作者：
S. T. Bradley;A. Young;L. Brillson;M. Murphy;W. Schaff;L. Eastman
我们使用低能电子激发纳米级发光光谱 (LEEN) 来检测 AlGaN/GaN HEMT 器件结构各层中的缺陷，并将其对二维电子气 (2-DEG) 限制的影响关联起来。我们使用 0.5 至 15 keV 的入射电子束能量研究了具有不同电特性的 AlGaN/GaN 异质结构，以探测每个异质结构层内的电子态跃迁。通过等离子体辅助分子束外延在蓝宝石衬底上的 GaN 缓冲层上生长的 25 nm 厚度和标称 30% Al 浓度的 AlGaN 异质结构表现出一系列极化诱导电子密度和室温迁移率。一般来说，光谱显示 AlGaN 带边发射在 /spl sim/3.8 eV 或 /spl sim/4.0 eV，GaN 带边发射在 /spl sim/3.4 eV，黄光 (YL) 特征在 2.18 eV 和 2.34 eV，以及来自用于钝化 AlGaN 外表面的 GaN 盖层的大量红外发射 (<1.6 eV)。这些异质结构还在 2 nm 厚的 GaN 层中表现出高应变，并有证据表明由于压电充电而出现 Franz-Keldysh 红移。 LEEN 深度剖面揭示了有和没有 2-DEG 限制的结构之间的差异，并强调了近 2-DEG 区域中 AlGaN 缺陷的重要性。
We have used low energy electron-excited nanoscale luminescence spectroscopy (LEEN) to detect the defects in each layer of AlGaN/GaN HEMT device structures and to correlate their effect on two-dimensional electron gas (2-DEG) confinement. We investigated AlGaN/GaN heterostructures with different electrical properties using incident electron beam energies of 0.5 to 15 keV to probe electronic state transitions within each of the heterostructure layers. AlGaN heterostructures of 25 nm thickness and nominal 30% Al concentration grown on GaN buffer layers on sapphire substrates by plasma-assisted molecular beam epitaxy exhibited a range of polarization-induced electron densities and room temperature mobilities. In general, the spectra exhibit AlGaN band edge emission at /spl sim/3.8 eV or /spl sim/4.0 eV, GaN band edge emission at /spl sim/3.4 eV, yellow luminescence (YL) features at 2.18 eV and 2.34 eV, and a large emission in the infrared (<1.6 eV) from the GaN cap layer used to passivate the AlGaN outer surface. These heterostructures also show high strain in the 2 nm-thick GaN layer with evidence for a Franz-Keldysh red shift due to piezoelectric charging. The LEEN depth profiles reveal differences between the structures with and without 2-DEG confinement and highlight the importance of AlGaN defects in the near 2-DEG region.