Accurate Small-Signal Equivalent Circuit Modeling of Resonant Tunneling Diodes to 110 GHz

This article presents a novel, on-wafer deembedding technique for the accurate small-signal equivalent circuit modeling of resonant tunneling diodes (RTDs). The approach is applicable to stabilized RTDs, and so enables the modeling of the negative differential resistance (NDR) region of the device's current-voltage (I-V) characteristics. Furthermore, a novel quasi-analytical procedure to determine all the equivalent circuit elements from the deembedded S-parameter data is developed. Extraction results of a 10 μm × 10 μm stabilized, low-current density RTD at different bias points show excellent fits between modeled and measured S-parameters up to 110 GHz.

I. Introduction

Over the last few decades, terahertz (THz) radiation, which has an electromagnetic spectrum that lies between millimeter-wave and infrared regions, has become a primary research interest in the fields of medical diagnostics, security imaging, and wireless communications [1]. The resonant tunneling diode (RTD) is a quantum-well structure, which exhibits a negative differential resistance (NDR) that extends to the THz range, thus making it one of the target candidates for such applications. There is intense on-going research on this device technology to realize compact and coherent THz sources [2]–[5]. Fundamental frequency oscillations at around 2 THz have recently been obtained from RTD oscillators [6]. Compared to other electronic device technologies that may be used in the 0.1–1 THz band such as transistors, Gunn diodes, etc., the RTD exhibits the largest bandwidth (for a given device size), requires simple circuitry, is compact, and consumes low power [7]. Recently, high-performance RTD-based THz short range multi-gigabit wireless links [8]–[10] and imaging applications have been demonstrated [11]. Thus, the accurate modeling of RTDs to support a reliable THz circuit design is of paramount importance.