Advances in molecular beam epitaxy (MBE) have been crucial for the engineering of heterostructures in which the wave nature of electrons dictates carrier transport dynamics. These advances led to the first demonstration of negative differential conductance (NDC) in arsenide-based resonant tunneling diodes (RTDs) in 1974. In contrast to the 17 years elapsed between the initial MBE growth of arsenide semiconductors and the first demonstration of room-temperature GaAs/AlAs RTDs, the development of polar III-nitride RTDs has been remarkably different. After pioneering growths of nitride materials by MBE in 1973, it would take 43 years—until 2016—to demonstrate the first GaN/AlN RTD that exhibits repeatable NDC at room temperature. Here, we discuss, from the crystal growth point of view, the key developments in the epitaxy of III-nitride heterostructures that have led us to the demonstration of robust resonant tunneling transport and reliable NDC in III-nitride semiconductors. We show that in situ tracking of the crystal electron diffraction allows us to deterministically control the number of monolayers incorporated into the tunneling barriers of the active region. Employing this technique, we fabricate various GaN/AlN RTD designs showing the exponential enhancement of the resonant tunneling current as a function of barrier thickness. In addition, we experimentally demonstrate that tunneling transport in nitride RTDs is sensitive to epitaxial parameters such as the substrate growth temperature and threading dislocation density. This new insight into the MBE growth of nitride resonant tunneling devices represents a significant step forward in the engineering of new functionalities within the family of III-nitride semiconductors, allowing to harness quantum interference effects for the new generation of electronic and photonic devices.

中文翻译：

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极性III氮化物共振隧穿二极管的分子束外延

分子束外延（MBE）的进展对于异质结构的工程设计至关重要，在异质结构中，电子的波动性质决定了载流子的传输动力学。这些进展导致1974年在基于砷化物的谐振隧穿二极管（RTD）中首次展示了负差分电导（NDC）。与从砷化物半导体的MBE初始生长到室温的首次展示之间相隔了17年。在GaAs / AlAs RTD方面，极性III氮化物RTD的开发已显着不同。在1973年MBE开创了氮化物材料的先驱之后，直到2016年，要证明第一个GaN / AlN RTD在室温下具有可重复的NDC，将需要43年的时间。在这里，我们从晶体生长的角度讨论，III型氮化物异质结构外延技术的关键发展已使我们展示了III型氮化物半导体中强大的共振隧穿传输和可靠的NDC。我们证明原位晶体电子衍射的跟踪使我们能够确定性地控制掺入到有源区的隧道势垒中的单层的数量。利用这项技术，我们制造了各种GaN / AlN RTD设计，这些设计显示了共振隧穿电流随势垒厚度的指数增长。此外，我们实验证明氮化物RTD中的隧穿传输对外延参数（例如衬底生长温度和螺纹位错密度）敏感。对氮化物共振隧穿器件的MBE增长的这种新见解，代表了III族氮化物半导体家族中新功能的工程设计迈出的重要一步，从而可以为新一代电子和光子器件利用量子干涉效应。