The effect of AlN interlayer thicknesses on scattering processes in lattice-matched AlInN/GaN two-dimensional electron gas heterostructures
The effect of AlN interlayer thicknesses on scattering processes in lattice-matched AlInN/GaN two-dimensional electron gas heterostructures
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DOI：
10.1088/1367-2630/11/6/063031
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发表时间：
2009-06
影响因子：
3.3
通讯作者：
A. Teke;S. Gökden;R. Tülek;Jacob H. Leach;Q. Fan;Jinqiao Xie;Ü. Özgür;Hadis Morkoç;S. B. Lişesi
中科院分区：
文献类型：
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作者：
A. Teke;S. Gökden;R. Tülek;Jacob H. Leach;Q. Fan;Jinqiao Xie;Ü. Özgür;Hadis Morkoç;S. B. Lişesi
研究了不同AIN间隔层厚度（0 ~ 2nm）的高迁移率AlInN/AlN/GaN二维电子气（2DEG）异质结构输运特性的散射机制。将声光声子、离子杂质、界面粗糙度、位错和合金无序等主要散射过程应用于温度相关迁移率数据。研究发现，当间隔层厚度达到0.3 nm时，主要由合金无序引起的散射限制了电子迁移率。另一方面，随着AlN间隔层厚度的进一步增加，合金散射大大减少，因此声、光学和界面粗糙度的组合在不同温度范围内具有不同程度的有效性。随着氮化铝间隔层的增加，室温电子迁移率逐渐增加。对于由1 nm AlN间隔层组成的样品，实现了1630 cm2 V−1 s−1的峰值电子迁移率。当AlN为2 nm时，电子迁移率降低。此外，测量的2DEG密度也与理论预测进行了比较，其中包括存在于AlN/GaN界面上的压电和自发极化成分。当考虑到在AlN和AlInN之间沉积的寄生（无意的）GaN层时，所有AlInN/AlN/GaN HEMT结构的实验载流子密度与理论预测非常吻合。从这些分析中，发现1 nm的AlN间隔层厚度是高电子迁移率所需的最佳厚度，因此一旦片载流子密度增加到没有无意GaN层的样品的理论期望值，则片电阻就会降低。
The scattering mechanisms governing the transport properties of high mobility AlInN/AlN/GaN two-dimensional electron gas (2DEG) heterostructures with various AIN spacer layer thicknesses from zero to 2 nm were presented. The major scattering processes including acoustic and optical phonons, ionized impurity, interface roughness, dislocation and alloy disorder were applied to the temperature-dependent mobility data. It was found that scattering due mainly to alloy disorder limits the electron mobility for samples having spacer layer thicknesses up to 0.3 nm. On the other hand, alloy scattering is greatly reduced as the AlN spacer layer thickness increases further, and hence the combination of acoustic, optical and interface roughness become operative with different degrees of effectiveness over different temperature ranges. The room-temperature electron mobility was observed to increase gradually as the AlN spacer layer increases. A peak electron mobility of 1630 cm2 V−1 s−1 was realized for the sample consisting of a 1 nm AlN spacer layer. Then, the electron mobility decreased for the sample with 2 nm AlN. Moreover, the measured 2DEG densities were also compared with the theoretical predictions, which include both piezoelectric and spontaneous polarization components existing at AlN/GaN interfaces. The experimental sheet carrier densities for all AlInN/AlN/GaN HEMT structures were found to be in excellent agreement with the theoretical predictions when the parasitic (unintentional) GaN layer deposited between AlN and AlInN was taken into account. From these analyses, 1 nm AlN spacer layer thickness is found to be the optimum thickness required for high electron mobility and hence low sheet resistance once the sheet carrier density is increased to the theoretically expected value for the sample without unintentional GaN layer.