Electronic transport of polarization-induced, two-dimensional electron gases with extremely high sheet carrier density for ScAlN/GaN-based power devices (ScNius)

该联合项目ScNius正在DFG优先计划“节能电力电子”中申请。其目的是研究具有极高界面电荷密度（> 1013 cm-2）的极化诱导二维电子气（2DEG）的电子输运性质，这些电子气被限制在ScAlN/GaN异质结构的界面处。基于对用于产生功率晶体管沟道的2DEG的主要散射机制的知识，将优化ScAlN/GaN异质结构的外延和设计，以最小化经处理的“高电子迁移率晶体管”（HEMT）的薄层电阻。在此基础上，我们将加工和展示与传统GaAlN/GaN HEMT相比具有显著提高的载流能力和能效的功率电子器件。在六个工作包中，将系统地相互构建，进行ScAlN/GaN异质结构和功率器件的外延，分析，技术，计量和模拟。该过程得到了申请人在GaN基功率电子器件的研究和开发以及六方ScxAl 1-xN层（0 ≤ x ≤ 0.45）的所有相关材料系数的确定方面的大量理论和实验初步工作的支持。借助金属有机化学气相沉积（MOCVD）技术，制备了高质量的ScAlN/GaN异质结构，并对其结构特性进行了分析。所获得的材料结构允许在ScAlN/GaN界面处具有极大的极化梯度，这将允许具有高达2·1013至6·1013 cm-2的电子密度和小于200 Ω/sq的薄层电阻的2DEG。然而，先前的工作表明，电子密度的增加降低了电荷载流子的迁移率。因此，本项目第一部分的工作重点是阐明2DEG的电输运性质和主要的散射机制。借助理论方法（薛定谔-泊松和蒙特卡罗模拟）和可用的电气测量技术，将确定与功率晶体管相关的物理特性，如迁移率，漂移和饱和速度。在此基础上，将确定合金和界面散射的影响以及点缺陷（例如带电点缺陷）和线缺陷（例如位错）的影响。所获得的知识，然后将被用来优化材料结构方面的最高可能的界面电荷密度和漂移速度的2DEG。

The joint project ScNius is being applied for within the DFG priority program "Energy Efficient Power Electronics". Its aim is to investigate the electronic transport properties of polarization-induced two-dimensional electron gases (2DEG) with extremely high interface charge densities (> 1013 cm-2), which are confined at the interface of ScAlN/GaN heterostructures. Based on the knowledge of the dominant scattering mechanisms for the 2DEGs creating the power transistor channel, the epitaxy and design of the ScAlN/GaN heterostructures will be optimized with respect to minimizing the sheet resistance of the processed "High Electron Mobility Transistors" (HEMTs). Based on this, power electronic devices with a significantly increased current-carrying capacity and energy efficiency compared to conventional GaAlN/GaN HEMTs are processed and demonstrated.In six work packages, systematically building upon each other, the epitaxy, analytics, technology, metrology, and simulation of ScAlN/GaN heterostructures and power devices will be performed. This procedure is supported by extensive theoretical and experimental preliminary work of the applicants in the research and development of GaN-based power electronic devices and the determination of all relevant material coefficients of hexagonal ScxAl1-xN layers (0 ≤ x ≤ 0.45). With the help of metal organic chemical vapor deposition (MOCVD), high quality ScAlN/GaN heterostructures are deposited and analyzed with respect to their structural properties. The obtained material structures allow enormously large polarization gradients at the ScAlN/GaN interface, which will allow 2DEGs with electron densities as high as 2·1013 to 6·1013 cm-2 and sheet resistances of less than 200 /sq. However, previous work shows that an increase in electron density decreases the mobility of the charge carriers. For this reason, the work in the first part of the project focuses on clarifying the electrical transport properties and the dominant scattering mechanisms of 2DEGs. With the help of theoretical methods (Schrödinger-Poisson and Monte Carlo simulations) and the available electrical measurement techniques, physical properties relevant for power transistors such as mobility, drift and saturation velocity will be determined. Based on these, the influence of alloy and interface scattering as well as the influence of point defects (e.g. charged point defects) and line defects (e.g. dislocations) will be ascertained. The gained knowledge will then be used to optimize the material structures with respect to the highest possible interface charge density and drift velocity of the 2DEGs.