Belio-Apaolaza Iñigo, Seddon James, Renaud Cyril C
Department of Electronic and Electrical Engineering, University College London, London, UK.
Sci Rep. 2025 Jul 1;15(1):21237. doi: 10.1038/s41598-025-05299-0.
Terahertz heterodyne receivers are essential for enabling coherent, high-sensitivity signal detection. At room temperature, GaAs Schottky barrier diodes remain the leading technology but present limitations, particularly in terms of high local oscillator power requirements and contact reproducibility. The fermi-level-managed barrier diode (FMBD), an all-semiconductor InGaAs/InP heterobarrier diode originally conceived for direct THz detection, has the potential to overcome these challenges. However, the intrinsic performance of the FMBD as a frequency mixer has not been fully reported, and there has been little analysis of how to optimise its epitaxial structure for heterodyne detection. In this study, we implement a semiconductor model to predict the nonlinear IV and CV characteristics of the FMBD based on its epitaxial layers, and conduct harmonic balance simulations to extract its intrinsic conversion loss and noise temperature. The results provide a guide for designing FMBD-based THz mixers, depending on the operating frequency, available LO power, and other design factors. In addition, we introduce a novel device concept: the fermi-level-managed multi-barrier diode (FMMBD), which consists of multiple concatenated heterobarriers. This design mitigates the trade-off between device area and junction capacitance. Simulations indicate the FMMBD improves device sensitivity, with intrinsic simulated noise temperatures approaching 10× the quantum limit.
太赫兹外差接收机对于实现相干、高灵敏度信号检测至关重要。在室温下，砷化镓肖特基势垒二极管仍是主流技术，但存在局限性，特别是在本地振荡器高功率要求和接触再现性方面。费米能级管理势垒二极管（FMBD）是一种最初为直接太赫兹检测而设计的全半导体铟镓砷/磷化铟异质势垒二极管，有潜力克服这些挑战。然而，FMBD作为混频器的固有性能尚未得到充分报道，并且对于如何优化其外延结构以用于外差检测的分析也很少。在本研究中，我们基于FMBD的外延层实现了一个半导体模型来预测其非线性电流 - 电压（IV）和电容 - 电压（CV）特性，并进行谐波平衡模拟以提取其固有变频损耗和噪声温度。结果根据工作频率、可用本地振荡器功率和其他设计因素，为设计基于FMBD的太赫兹混频器提供了指导。此外，我们引入了一种新颖的器件概念：费米能级管理多势垒二极管（FMMBD），它由多个串联的异质势垒组成。这种设计减轻了器件面积与结电容之间的权衡。模拟表明FMMBD提高了器件灵敏度，其固有模拟噪声温度接近量子极限的10倍。
