Frank Morris

Unified AC model for the resonant tunneling diode

A physics-based model is shown to yield the small-signal equivalent circuit of the resonant tunneling diode (RTD) including an analytic expression for both the quantum inductance and capacitance. This model unifies previous models by Brown et al. for quantum inductance and by Lake and Yang for quantum capacitance, and extends the RTD SPICE model of Broekaert. The equivalent circuit has been fit to both current-voltage and microwave S-parameter measurements of AlAs-InGaAs-InAs-InGaAs-AlAs RTDs from 45 MHz to 30 GHz and over biases from 0 to 0.81 V. Good agreement between the model and measurement is shown.

Resonant-tunneling mixed-signal circuit technology

Abstract A large-scale integration (LSI) InP-based technology is described for high-speed mixed-signal circuits. The monolithic 75-mm wafer process uses molecular beam epitaxy, InP etch stop layers, an electron-beam-defined gate, non-alloyed ohmic contacts, and 10 mask levels to provide resonant tunneling diodes (RTDs), 0.25- or 0.5-μm gate-length high electron mobility transistors (HEMTs), Schottky diodes, resistors, capacitors and two and a half levels of interconnect. Resonant tunneling circuits described here for the first time include a 2.5-GHz, ten stage, tapped shift register, a 6.5-GHz clock generator and a multivalued-to-binary converter.

Zero bias resonant tunnel Schottky contact diode for wide-band direct detection

A Schottky-collector resonant tunnel diode detector has been fabricated and characterized at zero bias up to 400 GHz. General device structure and fabrication are discussed, and small-signal equivalent models are presented for different diode areas. Over the measured range of 200 to 400 GHz using a monolithic antenna structure, noise equivalent power values between 3-8 pW/Hz/sup 1/2/ are achieved. The current-voltage characteristics of the diode show weak temperature dependence over a measured range of 213-323 K.

Resonant tunneling circuit technology: has it arrived?

A three-dimensional large-scale integration (LSI) process for fabrication of resonant tunneling diodes and heterojunction field-effect transistors on InP has been demonstrated, combining two of todays fastest semiconductor devices. Demonstrations of this technology now include multigigahertz digital and mixed-signal circuits and ultralow power SRAM circuits; 25 to 100 GHz circuits are clearly in range for this technology.

Schottky barrier contact-based RF MEMS switch

This paper presents the design, fabrication and measurement results for a novel Schottky barrier contact-based RF MEMS switch. This Schottky barrier contact allows one to operate the RF MEMS switch in a traditional capacitive mode when it is reverse biased, but can also conduct current in a forward biased state. Forward biasing the switch recombines trapped charges, thus extending the lifetime of the switch. This work intimately combines MEMS processing with solid-state electronics to produce a truly unique RF device. To the authors knowledge, nothing similar to this work has ever been reported.

50 GHz resonant tunneling diode relaxation oscillator

InAlAs/AlAs based RTDs with a peak current density over 500 kA/cm/sup 2/ have been designed and fabricated. Relaxation oscillator circuits for 20 and 50 GHz were designed using these 0.6 /spl mu/m/sup 2/ RTDs. They consist of an RTD and a 5 /spl Omega/ resistor placed in a coplanar waveguide (CPW). The measured spectrum of the 20 GHz and 50 GHz oscillators showed only odd harmonics. The measured results of the relaxation oscillators show that they have very low phase noise (low jitter), below -110 dBc/Hz at 1 MHz offset in locked-mode, and can easily be phase locked. RTD based relaxation oscillation can be readily used as clocks in high-speed signal processing applications.

Schottky Contact RF MEMS Switch Characterization

This paper presents measured results for a novel Schottky barrier contact-based RF MEMS switch, specifically S-parameter and IP2 linearity measurements. The Schottky barrier contact allows one to operate the RF MEMS switch in a traditional capacitive mode when it is reverse biased, but can also conduct current in a forward biased state to discharge trapped charges. This configuration improves reliability, but increases insertion loss. This work intimately combines MEMS processing with solid-state electronics to produce a truly unique RF device. To the authors knowledge, nothing similar to this work has ever been reported.

Resonant tunneling technology for mixed signal and digital circuits in the 10-100 GHz domain

The inherent bistability and picosecond time-scale switching of the resonant tunneling diode (RTD) provides an ideal element for the design of digital circuits and analog signal quantizers in the 10-100 GHz domain. New differential RTD-based circuits for quantizers and a first-order sigma-delta modulator capable of operating at 10 GHz and beyond are introduced.

Schottky Barrier Contact-Based RF MEMS Switch

This paper presents the design, fabrication, and measurement results for a novel Schottky barrier contact-based radio frequency (RF) microelectromechanical systems (MEMS) switch. This Schottky barrier contact allows one not only to operate the RF MEMS switch in a traditional capacitive mode when it is reverse biased but also conduct current in a forward biased state. Forward biasing the switch recombines trapped charges, thus extending the lifetime of the switch. This paper intimately combines MEMS processing with solid-state electronics to produce a truly unique RF device.

Monolithic 4 bit 2 GSps resonant tunneling analog-to-digital converter

The combination of resonant tunneling diodes (RTDs) and heterostructure field-effect transistors (HFETs) provides a versatile technology for implementing microwave digital and mixed-signal applications. Here we demonstrate the first monolithic flash RTD/HFET analog-to-digital converter (ADC). The first pass ADC achieved 2.7 effective bits at 2 GSps. The one bit quantizer achieved a single tone spurious free dynamic range (SFDR) of greater than 40 dB at 2 GSps for a 220 MHz single tone input with dithering.