G. I. Haddad

Power and stability limitations of resonant tunneling diodes

Stability criteria for resonant tunneling diodes are investigated. Details of how extrinsic elements, such as series inductance and parallel capacitance, affect the stability are presented. A GaAs/AlAs/InGaAs/AlAs/GaAs double-barrier diode is investigated, showing the effect of different modes of low-frequency oscillation and the extrinsic circuit required for stabilization. The effect of device stabilization on high-frequency power generation is described. The main conclusions of the paper are: (1) stable resonant tunneling diode operation is difficult to obtain, and (2) the circuit and device conditions required for stable operation greatly reduce the amount of power that can be produced by these devices. >

Design, modeling, and characterization of monolithically integrated InP-based (1.55 /spl mu/m) high-speed (24 Gb/s) p-i-n/HBT front-end photoreceivers

High-speed, long-wavelength InAlAs/InGaAs OEIC photoreceivers based on a p-i-n/HBT shared layer integration scheme have been designed, fabricated and characterized. The p-i-n photodiodes, formed with the 6000 /spl Aring/-thick InGaAs precollector layer of the HBT as the absorbing layer, exhibited a responsivity of /spl sim/0.4 A/W and a -3 dB optical bandwidth larger than 20 GHz at /spl lambda/=1.55 /spl mu/m. The fabricated three-stage transimpedance amplifier with a feedback resistor of 550 /spl Omega/ demonstrated a transimpedance gain of 46 dB/spl Omega/ and a -3 dB bandwidth of 20 GHz. The monolithically integrated photoreceiver with a 83 /spl mu/m p-i-n photodiode consumed a small dc power of 35 mW and demonstrated a measured -3 dB optical bandwidth of 19.5 GHz, which is the highest reported to date for an InAlAs/InGaAs integrated front-end photoreceiver. The OEIC photoreceiver also has a measured input optical dynamic range of 20 dB. The performance of individual devices and integrated circuits was also investigated through detailed CAD-based analysis and characterization. Transient simulations, based on a HSPICE circuit model and previous measurements of eye diagrams for a NRZ 2/sup 31/-1 pseudorandom binary sequence (PRBS), show that the OEIC photoreceiver is capable of operation up to 24 Gb/s.

Time‐dependent modeling of resonant‐tunneling diodes from direct solution of the Schrödinger equation

Numerical solution of the time‐dependent Schrodinger equation for resonant‐tunneling diodes has been impeded by the difficulty in handling open‐system boundary conditions. This paper presents a boundary condition method to simulate the interaction with ideal particle reservoirs at the device boundaries. A switching transient is calculated where the device is switched from the peak current state to the valley current state. In addition, this method was used to develop a small‐signal analysis of resonant‐tunneling diodes. Results for the small‐signal equivalent circuit of a particular device versus frequency are presented.

Transfer matrix method for interface optical-phonon modes in multiple-interface heterostructure systems

Interactions of carriers with interface optical phonons dominate over other carrier–phonon scatterings in narrow quantum-well structures. Herein, a transfer matrix method is used to establish a formalism for determining the dispersion relations, electrostatic potentials, and Frohlich interaction Hamiltonians of the interface optical phonons for multiple-interface heterostructure systems within the framework of the macroscopic dielectric continuum model. This method facilitates systematic calculations for complex structures where the conventional method is very difficult to implement. Several specific cases are treated to illustrate the advantages of the general formalism.

Wigner-function modeling of resonant tunneling diodes with high peak-to-valley ratios

Wigner function simulations of structures with experimentally observed high peak‐to‐valley ratios are carried out. It is shown that if care is taken with the numerical method used, the simulations reproduce these sharp resonances. When scattering is ignored, peak‐to‐valley ratios of 33.7 are obtained for a pseudomorphic InGaAs‐AlAs structure. The effects of phonon scattering are included to first order. Also, a small‐signal analysis is carried out and the results are used to predict the rf power generation capability of these devices.

Observation of intrinsic bistability in resonant tunneling diode modeling

Intrinsic bistability has been observed experimentally and attributed to the effect on the potential profile from stored charge in the quantum well through Poisson’s equation. This effect leads to two possible current states corresponding to a single voltage within the negative resistance region. In this letter a simulation method is presented which clearly shows bistability in the current‐voltage curve of a resonant tunneling diode. This method self‐consistently combines a Thomas–Fermi equilibrium model for the electron concentrations outside the double‐barrier structure with a quantum calculation for the concentration inside the structure.

Metal‐Oxide‐Metal (M‐O‐M) Detector

The properties of a metal‐oxide‐metal (M‐O‐M) tunneling detector are presented and the parameters influencing its operation are discussed. The theory of operation and experimental results for small as well as large signals are presented. The polarity reversal at large‐signal levels is predicted theoretically and observed experimentally.

C-V and I-V characteristics of quantum well varactors

A theoretical model for quantum well varactors is presented. The model is used to calculate the device C‐V and I‐V characteristics and very good agreement has been found between the calculated and measured results. Based on the model, a triple barrier double well varactor has been designed and fabricated. A very high capacitance ratio within a very small bias range is achieved, as designed. Details of the design calculations and experimental results are presented.

16-GHz bandwidth InAlAs-InGaAs monolithically integrated p-i-n/HBT photoreceiver

A monolithically integrated p-i-n transimpedance-amplifier photoreceiver based on an InAlAs-InGaAs HBT structure lattice-matched to InP has been designed, fabricated, and characterized. The p-i-n photodiode is implemented using the InGaAs base and collector layers of the HBT. A three-stage amplifier with a feedback resistance of 550 /spl Omega/ demonstrated a transimpedance gain of 46 dB/spl Omega/ and a bandwidth of 20 GHz, corresponding to a transimpedance-bandwidth product of 4 THz/spl Omega/. The measured -3 dB bandwidth of the integrated photoreceiver is 16 GHz, which is the highest reported to date for an InAlAs-InGaAs p-i-n/HBT monolithically integrated photoreceiver and is sufficient for 20-Gb/s operation.<<ETX>>

Phonon assisted intersubband transitions in step quantum well structures

We evaluate effects of heterointerfaces on optical phonon modes and phonon assisted electron intersubband transition rates in step quantum well structures for intersubband lasers. Various phonon modes and electron–phonon interaction Hamiltonians, including the interface modes, confined longitudinal-optical modes, and half space modes in the quantum well structures are calculated based on the macroscopic dielectric continuum model and microscopic analysis. The transfer matrix method is used to calculate the interface modes. The intersubband transition rates due to electron–phonon scattering by these phonon modes are evaluated using Fermi’s golden rule, with the electron wave functions obtained by solving the Schrodinger equation for the heterostructures under investigation. Our results show that, compared with the transition rates in the same structures calculated using the bulk phonon modes and the bulk Frohlich interaction Hamiltonian, the electron interface–phonon interactions give significantly larger ...