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首页> 外文会议>Conference on gallium nitride materials and devices IV; 20090126-29; San Jose, CA(US) >Two dimensional electron gas in GaN heterojunction field effect transistors structures with AlN spacer
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Two dimensional electron gas in GaN heterojunction field effect transistors structures with AlN spacer

机译：具有AlN隔离层的GaN异质结场效应晶体管结构中的二维电子气

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摘要

Near lattice matched Al_(0.81)In_(0.19)N/GaN heterojunction structures are compared with conventional Al_(0.3)Ga_(0.7)N/GaN heterojunctions in terms of the sheet density and mobility and their dependence on barrier and spacer layer parameters. With the insertion of an A1N spacer, the mobility of both structures is improved dramatically. Self-consistent solution of Poisson-Schrodinger equations was developed in order to determine the band structure and carrier distribution in these GaN based heterostructures in an effort to gain insight into the experimental observations. Surface donor states were included to account for the origin of electrons in 2DEG, which is treated as charge neutralization conditions in the simulation. Also the change in the piezoelectric polarization due to the electromechanical coupling effect, and shift of band gap caused by uniaxial strain were both included in the calculations. The calculated sheet density is close to the measured values, especially for the AlGaN samples investigated, but a notable difference was noted in the AlInN cases. The discrepancy is confirmed to be caused by the existence of a Ga-rich layer on the top of A1N spacer during the growth interruption, which can split the 2DEG into two channels with different mobilities and lower the overall sheet density. When the modifications made necessary by this GaN layer are taken into account in our model for the AlInN barrier case, the calculations match with the experimental data. When the spacer thickness increase from 0.3 to 3 nm, the total sheet density was found to slightly increase experimentally, which agreed with the theoretical prediction.
机译：就薄层密度和迁移率及其对势垒和间隔层参数的依赖性而言，将近晶格匹配的Al_（0.81）In_（0.19）N / GaN异质结结构与常规Al_（0.3）Ga_（0.7）N / GaN异质结进行了比较。通过插入AlN隔离层，两种结构的迁移率都得到了显着提高。为了确定这些基于GaN的异质结构中的能带结构和载流子分布，研究人员开发了Poisson-Schrodinger方程的自洽解，以期深入了解实验观察结果。包括表面给体状态以说明2DEG中电子的起源，在模拟中将其视为电荷中和条件。计算中还包括由于机电耦合效应引起的压电极化变化以及由单轴应变引起的带隙位移。计算出的薄层密度接近于测量值，尤其是对于所研究的AlGaN样品，但是在AlInN情况下却注意到了显着差异。确认该差异是由于生长中断期间AlN间隔层顶部存在富Ga层引起的，该富Ga层可以将2DEG分为两个具有不同迁移率的通道，并降低了总的纸张密度。当在我们的模型中考虑到AlInN势垒情况下，需要考虑此GaN层进行必要的修改时，计算结果与实验数据相符。当垫片厚度从0.3纳米增加到3纳米时，实验发现总片材密度略有增加，这与理论预测相符。

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