A. L. Gutierrez-Aitken

Tunneling injection lasers: a new class of lasers with reduced hot carrier effects

In conventional quantum-well lasers, carriers are injected into the quantum wells with quite high energies. We have investigated quantum-well lasers in which electrons are injected into the quantum-well ground state through tunneling. The tunneling injection lasers are shown to have negligible gain compression, superior high-temperature performance, lower Auger recombination and wavelength chirp, and better modulation characteristics when compared to conventional lasers. The underlying physical principles behind the superior performance are also explored, and calculations and measurements of relaxation times in quantum wells have been made. Experimental results are presented for lasers made with a variety of material systems, InGaAs-GaAs-AlGaAs, InGaAs-GaAs-InGaAsP-InGaP, and InGaAs-InGaAsP-InP, for different applications. Both single quantum-well and multiple quantum-well tunneling injection lasers are demonstrated.

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.

A "cold" InP-based tunneling injection laser with greatly reduced Auger recombination and temperature dependence

We have measured the Auger recombination rates in an InP-based quantum well tunneling injection laser from large signal modulation experiments. Measured values of the Auger coefficient, C/sub o/=1.2/spl plusmn/0.6/spl times/10/sup -29/ cm/sup 6/ s/sup -1/ at 283 K, are a factor of over 10/sup 2/ smaller than those measured in similar multiple quantum well separate confinement heterostructure lasers. In effect, the tunneling injection mechanism keeps the carriers cold even at high injection levels. A maximum value of T/sub o/=70 K is measured in the tunneling injection laser compared to 50 K for conventional quantum well structures,.<<ETX>>

Responsivity and impact ionization coefficients of Si/sub 1-x/Ge/sub x/ photodiodes

The spectral response and impact ionization coefficient ratio of Si/sub 1-x/Ge/sub x/ have been determined. Measurements were made on p/sup +/-i-n/sup +/ diodes grown by solid/gas source molecular beam epitaxy. The diodes are characterized by reverse breakdown voltages of 4-12 V and dark currents of 20-170 pA//spl mu/m/sup 2/. The long wavelength cut-off of the diodes increases from 1.2 /spl mu/m to 1.6 /spl mu/m as x increases from 0.08 to 1.0 with a maximum responsivity of 0.5 A/W in all the diodes tested. The ratio /spl alpha///spl beta/ varies from 3.3 to 0.3 in the same composition range, with /spl alpha///spl beta/=1 at x/spl cong/0.45. These results have important implications in the use of this material system in various photodetection applications.

An HSPICE HBT model for InP-based single HBTs

An HBT model for InP-based single HBTs (SHBTs) was developed based on the conventional Gummel-Poon large-signal BJT model available in HSPICE. Several typical characteristics observed from InP-based SHBTs, such as soft breakdown and collector transit-time delay effects, were modeled through a macro modeling approach. Excellent agreement has been achieved between the experimental and calculated results based on the model.

GaAs‐based multiple quantum well tunneling injection lasers

We report the modulation characteristics of multiple quantum well tunneling injection lasers designed for 0.98 μm emission wavelength. Electrons are injected into the active region through a single barrier via tunneling. The active region has four quantum wells with different well widths. Improved high frequency performance, compared to similar separate confinement heterostructure lasers, has been demonstrated. The modulation response at 21 GHz is above 0 dB and the extrapolated −3 dB modulation bandwidth is ∼30 GHz under pulsed bias.

SPICE-based DC and microwave characterization of InAlAs/InGaAs HBTs used for large-bandwidth integrated transimpedance amplifiers

The DC and small-signal microwave performance of InAlAs/InGaAs single HBTs (SHBTs) used for large-bandwidth monolithically integrated transimpedance amplifiers is characterized based on a new HBT model built in SPICE. Several effects observed from InGaAs SHBTs, which are not accounted for in the conventional Gummel-Poon BJT model, are modeled through a macromodeling approach. The developed HBT model accompanied by a detailed parameter-extraction process predicts accurately measured DC and AC characteristics of the HBTs and transimpedance amplifiers.

Impact ionization coefficients in Si1−xGex

We have measured the electron and hole impact ionization coefficients in Si1−xGex alloys. Carrier multiplication measurements were made on relaxed Si1−xGex/Si diodes grown by gas source molecular beam epitaxy. The hole to electron impact ionization coefficient ratio, β/α, varies from 0.3 to 4 in the composition range of x=0.08–1.0.

High-speed InP-based strained MQW ridge waveguide laser

A high-speed ridge waveguide laser with undoped strained MQW active region was fabricated and characterized. The lasers demonstrated typical threshold currents of /spl sim/20 mA. The electrical impedance of the laser demonstrates -3 dB bandwidths >34 GHz at high bias currents, indicating that the parasitics in our devices are very small. The best laser demonstrated a -3 dB modulation bandwidth of 20 GHz. This is the highest bandwidth achieved for a ridge waveguide laser operating at 1.55 /spl mu/m.

16-channel monolithically integrated InP-based p-i-n/HBT photoreceiver array with 11-GHz channel bandwidth and low cross talk

High-performance multichannel detection systems are required for wavelength-division multiplexed (WDM) communication systems. In the present work, we report a 16-channel InAlAs-InGaAs optoelectronic integrated circuits (OEIC) photoreceiver array with an average channel bandwidth of 11 GHz. To our knowledge, the fabricated array is the largest in size and exhibits the highest bandwidth per channel and lowest cross talk for any monolithic photoreceiver array for WDM applications.