M.J. Mondry

Monolithic Schottky-collector resonant tunnel diode oscillator arrays to 650 GHz

We report monolithic array oscillators incorporating Schottky-collector resonant tunnel diodes (SRTDs). In the SRTD, a 0.1-/spl mu/m width Schottky collector contact provides a greatly reduced device series resistance, resulting in an estimated 2.2 THz maximum frequency of oscillation. A 64-element oscillator array oscillated at 650 GHz while a 16-element array produced 28 /spl mu/W at 290 GHz.

Refractive indexes of (Al,Ga,In)As epilayers on InP for optoelectronic applications

Molecular beam epitaxy (MBE)-grown bulk and short-period superlattices of (Al,Ga,In)As epilayers lattice matched to InP were characterized by double-crystal diffractometry and low-temperature photoluminescence. A reflection spectroscopy technique was used to determine the refractive index of (Al,Ga,In)As films as a function of wavelength. The measured data were fitted to a single-oscillator dispersion model, and the model coefficients are given. The resulting expression can be used in the design of waveguides, modulators, and other optical devices.<<ETX>>

SILICON HETEROINTERFACE PHOTODETECTOR

We report the demonstration of an infrared avalanche photodetector that uses an InGaAs absorption layer and a Si avalanche multiplication layer bonded by wafer fusion. Photocurrent measurements of the silicon heterointerface photodetector showed high response to 1.3 μm light and gains of up to 130. Frequency response measurements for the detectors yielded 3 dB bandwidth products of up to 81 GHz.

Transferred substrate Schottky-collector heterojunction bipolar transistors: first results and scaling laws for high f/sub max/

Unlike normal heterojunction bipolar transistors (HBTs), transferred substrate Schottky-collector HBTs (SCHBTs) exhibit substantial increases in f/sub max/ as the emitter and collector stripes are scaled to deep submicron dimensions. First generation InAlAs/InGaAs SCHBTs with aligned 1-/spl mu/m emitter and collector stripes have been fabricated.<<ETX>>

Impurity-free disordering of InGaAs/InGaAlAs quantum wells on InP by dielectric thin cap films and characterization of its in-plane spatial resolution

We have studied impurity-free disordering of InGaAs/InGaAlAs quantum wells on InP, induced by three different dielectric cap films, namely, SiO2, SiNx and SrF2. The difference in photoluminescence characteristics of these materials after heat treatment has been discussed. Furthermore, the in-plane spatial resolution of the disordering process has been investigated for the first time.

Photonic integrated tunable receivers with optical preamplifiers for direct detection

We propose and demonstrate a photonic integrated tunable receiver which cascades a traveling‐wave optical preamplifier, a passive tunable grating‐assisted codirectional coupler filter, and a waveguide photodetector. The devices contain three strained InGaAs quantum wells and operate around λ=0.98 μm. The spectral responses have been measured using the broadband spontaneous emission from the integrated amplifier. Optical filters ∼4‐nm wide, ∼10‐nm apart with grating pitches ranging from 7.4 to 10.6 μm were observed. Wavelength selective photodetection of a channel ∼3‐nm wide, tunable over 4.3 nm with a reverse bias is in relatively good agreement with theory.

Monolithic integration of refractive lenses with vertical-cavity lasers and detectors for optical interconnections

We present a technique for monolithic integration of vertical cavity lasers and detectors with refractive microlenses etched on the back side of the semiconductor substrate in a wafer-scale process. This integration provides collimated or focused laser beam sources for applications in free-space interconnections or for coupling to optical fibers, and it improves the collection efficiency of detectors.

Monolithic integrated resonant tunneling diode and heterostructure junction field effect transistor circuits

Abstract We have developed a simple technology for monolithic integration of resonant tunneling diodes (RTDs) and heterostructure junction-modulated field effect transistors (HJFETs). We have achieved good device performance with this technology: HJFETs had transconductances of 290 mS/mm and current densities of 310 mA/mm for a 1.5 μm gate length; RTDs had room temperature peak to valley ratios greater than 20:1 with current densities of 42 kA/cm2. With this technology, we have demonstrated a monolithically integrated RTD + HJFET state holding circuit that can serve as a building block circuit for self-timed logic units. This circuit is resistor-free and operates at room temperature. The state holding circuit showed large noise margins of 1.21 V and 0.71 V, respectively, for input low and input high, for a 1.7 V input voltage swing. We have examined the transient response of the circuit and investigated the effect of circuit design parameters on propagation delay. We identify the RTD valley current as the limiting factor on propagation delay. We discuss the suitability of RTD + HJFET circuits such as our state holding circuit for highly dense integrated circuits.

Silicon hetero-interface photodetector

We propose and demonstrate a novel avalanche photodetector that uses separate InGaAs absorption and Si multiplication regions fabricated by wafer fusion. Directly integrating InGaAs and silicon layers in an avalanche photodetector combines the high long-wavelength absorption capabilities of InGaAs and the avalanche multiplication properties of Si. The large ratio of electron and hole ionization coefficients of silicon results in lower noise and a higher gain bandwidth product than achievable using III-V semiconductors in avalanche regions.

Molecular beam epitaxial growth of strained AlGaInAs multi-quantum well lasers on InP

State of the art transparency currents as low as 41 A/cm2per well have been achieved in strained AIGalnAs multi-quantum well (MQW) 1.5 urn lasers. Grown by solid source molecular beam epitaxy, broad area lasers with seven quantum wells exhibit threshold current densities of less than 900 A/cm2 for a 300 μm device length, comparable to the best results in this material system by any growth technology. The key to this threshold current density reduction is the optimization of the quantum well width. Experimentally, we found that thresh-old current densities can be reduced by a factor of two by using MQW active regions with wider wells which we attribute to a reduction in the nonradiative recombination and improved electron-hole overlap. High resolution x-ray diffraction, photoluminescence, and broad area lasers were used to characterize the MQW active regions.