Collaborative Research: SiGeSn-based heterostructures for intersubband photonic materials

非技术描述：该项目的目标是研究和开发一种基于硅、锗和锡合金（SiGeSn）的新型半导体材料系统。这项活动建立在一个团队为各种近红外和中红外光子器件（如激光器和光电探测器）开发SiGeSn材料的专业知识的基础上。理论工作预测，SiGeSn材料可以在与锗（Ge）层交替的原子尖堆叠中生长，以形成量子阱，其电子能级可以通过设计来设计，从而在电磁波谱的未开发部分（超长波长红外和太赫兹）中产生光学响应。此外，由于材料的每个组成原子都位于元素周期表的同一列（第四族），晶体的振动不会产生电偶极子，因此不会与光和电子发生太多相互作用——这是一个非常有益的特性。进行基础研究是为了(a)在具有原子尖锐界面的层状堆叠中生长SiGeSn材料的特定成分，(b)表征此类材料的基本电子特性，以及(c)在概念验证演示中显示远红外光学跃迁可以根据我们的设计进行工程设计。如果成功，这项工作将为新的远红外和太赫兹激光器和光电探测器奠定基础，从而充分利用电磁频谱。除了研究生和本科生的参与外，一名首席研究员还参与了一项研究项目课程，该课程旨在招募和保留代表性不足的少数民族一年级工程专业学生，而另一名首席研究员则从当地的HBCU招募相关学生。这种新的半导体材料系统与主流硅半导体技术高度兼容，这将有助于向工业过渡，并将推动未来美国半导体制造业的利益。技术描述：本项目的研究目标是在中红外和远红外光谱范围内，研究晶格匹配Ge/SiGeSn异质结构量子阱作为n型子带间光电器件的新材料体系。其动机在于这种iv族半导体是非极性的，这导致与广泛用于子带间器件的III-V异质结构相比，光学声子相互作用的特征显着不同。例如，(a)子带间电子-声子非辐射散射显著减少，(b)与雷斯特拉赫伦带相关的光学声子对光的强吸收显著减少。如果成功开发，这种材料系统可能导致在室温下以低功耗工作的太赫兹量子级联激光器；远、中红外高灵敏度量子阱红外光电探测器；利用IV族半导体器件新达到30-60微米远红外波长的能力，这是传统III-V族材料无法达到的。该研究包括在材料生长和表征、太赫兹和远红外子带间光学光谱方面的互补努力，并最终在基于子带间光导的概念验证演示中达到高潮。用于红外和太赫兹光子学的SiGeSn材料系统的开发为在300毫米晶圆上基于代工厂的器件生长提供了可能性，并与中红外的下一代集成“硅”光子平台集成。这有可能使传感、热成像、通信和光谱学等领域的许多应用受益。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical description:The goal of this project is to study and develop a new semiconductor material system based upon alloys of silicon, germanium, and tin (SiGeSn). This activity builds upon the expertise of one of the team in developing SiGeSn materials for a variety of photonic devices in the near- and mid-infrared (such as lasers and photodetectors). Theoretical work has predicted that SiGeSn materials could be grown in alternating atomically sharp stacks with germanium (Ge) layers to make sets of quantum wells whose electronic energy levels can be engineered by design to give an optical response in an undeveloped part of the electromagnetic spectrum: the very long wavelength infrared and the terahertz. Furthermore, due to the fact that each of the constituent atoms of the material resides in the same column of the periodic table (Group IV), the vibrations of the crystal do not induce electric dipoles and hence will not interact much with light and electrons – a highly beneficial property. Fundamental studies are pursued to (a) grow the specific compositions of the SiGeSn material in layered stacks with atomically sharp interfaces, (b) characterize the fundamental electronic properties of such materials, and (c) show in a proof-of-concept demonstration that a far-infrared optical transition can be engineered according to our designs. If successful, this work lays the foundation for new far-infrared and terahertz lasers and photodetectors so as to fully exploit the electromagnetic spectrum. In addition to the involvement of graduate and undergraduate students, one principal investigator participates in a research projects course designed for the recruitment and retention of underrepresented minority first-year engineering students, and the other principal investigator recruits involved students from a local HBCU. This new semiconductor material system is highly compatible with mainstream silicon semiconductor technology, which will ease transition to industry and will advance future US semiconductor manufacturing interests. Technical description:The research goal of this project is to investigate lattice-matched Ge/SiGeSn heterostructure quantum wells as a new material system for n-type intersubband optoelectronic devices in the mid-infrared and far-infrared spectral range. The motivation lies in the fact that such group-IV semiconductors are non-polar, which results in a dramatically different character of the optical phonon interactions compared with III-V heterostructures widely used for intersubband devices. For example, (a) there is dramatically reduced intersubband electron-phonon nonradiative scattering and (b) drastic reduction of the strong absorption of light by optical phonons associated with the Reststrahlen band. If successfully developed, this material system could lead to terahertz quantum-cascade lasers that operate at room-temperature with low power consumption; high-sensitivity quantum-well infrared photodetectors in the far- and mid-infrared; the ability to newly reach the far-infrared wavelengths of 30-60 microns with group IV semiconductor devices not accessible with conventional III-V materials. The research comprises complementary efforts in materials growth and characterization, THz and far-infrared intersubband optical spectroscopy, and culminating in a proof-of-concept demonstration of intersubband based photoconductivity. Development of the SiGeSn material system for infrared and THz photonics opens the possibility of foundry-based growth of devices on 300-mm wafers, and integration with next generation integrated “silicon” photonic platforms in the mid-infrared. This has the potential to benefit many applications in sensing, thermal imaging, communications, and spectroscopy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.