B.C. Johnson

Electric field screening by photogenerated holes in multiple quantum wells : a new mechanism for absorption saturation

We observe saturation in the electroabsorption of InGaAs/InP multiple quantum wells (MQWs) at high optical intensity. Contrary to the mechanism for zero‐field MQWs, we find that saturation occurs due to the presence of trapped photogenerated holes that screen the MQWs from the applied electric field. By carefully measuring the absorption coefficient of the wells and the emission time for holes, we are able to fit the observed electroabsorption saturation with no adjustable parameters.

Multiplication noise of wide-bandwidth InP/InGaAsP/InGaAs avalanche photodiodes

Measurements of InP/InGaAsP/InGaAs separate absorption, grading, and multiplication avalanche photodiode multiplication indicate that at high gains the excess noise factors approach values predicted by the conventional continuum theory. However, at lower gains the noise is suppressed. This is probably an artifact of the very thin multiplication layers which have been used to increase the gain-bandwidth product. From the frequency response of the noise power, a gain-bandwidth product of 60 GHz, which is consistent with the value of 57 GHz obtained directly from bandwidth measurements, is deduced. >

Frequency response of InP/InGaAsP/InGaAs avalanche photodiodes

A theoretical model for the frequency response of InP/InGaAs avalanche photodiodes (APDs) is presented. Included in the analysis are resistive, capacitive, and inductive parasitics, transit-time factors, hole trapping at the heterojunction interfaces, and the avalanche buildup time. The contributions of the primary electrons, primary holes, and secondary electrons to the transit-time-limited response are considered separately. Using a measurement apparatus which consists of a frequency synthesizer and a spectrum analyzer controlled by a microcomputer, the frequency response of InP/InGaAsP/InGaAs APDs grown by chemical-beam epitaxy are measured. Good agreement with the calculated response has been obtained over a wide range of gains. >

High-speed InP/InGaAsP/InGaAs avalanche photodiodes grown by chemical beam epitaxy

High-performance InP/InGaAsP/InGaAs avalanche photodiodes (APDs) grown by chemical beam epitaxy are described. These APDs exhibit low dark current (less than 50 nA at 90% of breakdown), good external quantum efficiency (greater than 90% at a wavelength of 1.3 mu m), and high avalanche gain ( approximately=40). In the low-gain regime, bandwidths as high as 8 GHz have been achieved. At higher gains, a gain-bandwidth-limited response is observed; the gain-bandwidth product is 70 GHz. >

Gain recovery time of traveling-wave semiconductor optical amplifiers

We propose a mechanism which may shorten the gain recovery time in semiconductor optical amplifiers. The mechanism is carrier diffusion from nearby carrier storage regions (carrier reservoirs), which enhances the carrier recovery process in the active region and consequently reduces the gain recovery time. Bias‐independent recovery times as short at 100 ps are demonstrated in a 1.3‐μm traveling‐wave amplifier.

An InP/InGaAs p-i-n/HBT monolithic transimpedance photoreceiver

A monolithically integrated 1-Gb/s p-i-n/HBT transimpedance photoreceiver is discussed. The optoelectronic integrated circuit (OEIC) was made from metalorganic vapor-phase epitaxy (MOVPE)-grown InP/InGaAs heterostructures and had a transimpedance of 1375 Omega , a sensitivity of -26.1 dBm, >25-dB dynamic range, and a 500-MHz bandwidth.<<ETX>>

Disordering of InGaAs‐InP quantum wells by Si implantation

Selective disordering of In0.53Ga0.47As‐InP multiple quantum well structures by ion implantation is demonstrated for the first time. As grown, annealed, and Si implanted and annealed samples were studied by transmission electron microscopy, optical absorption, and photoluminescence. A shift of the photoluminescence and absorption edge to higher energy was observed in implanted and annealed samples with respect to annealed only samples. This shift is attributed to a combination of disordering and Burstein–Moss effect.

A monolithic long wavelength photoreceiver using heterojunction bipolar transistors

An optoelectronic integrated circuit (OEIC), consisting of a p-i-n photodetector and heterojunction bipolar transistors connected together as a transimpedance photoreceiver, has been fabricated. The monolithic photoreceiver was made from InP/InGaAs-based heterostructures and had a bandwidth of 500 MHz with a transimpedance of 1375 Omega . At a signaling rate of 1 Gb/s, the measured receiver sensitivity was -26.1 dBm at a wavelength of 1.5 mu m. A dynamic range greater than 25 dB and an equivalent input noise current of 11 pA square root Hz were also measured. >

Interaction of hole trapping and transit effects in the temporal response of InP/InGaAs p‐type insulator n‐type photodiodes

Photodiodes with thin (∼0.2 μm) InGaAs light absorbing layers placed inside much wider (∼2 μm)InP depletion regions were studied to understand the interaction of hole trapping at the InGaAs/InP heterojunction interface and carrier transit effects. In the three devices studied, the absorbing region was located (i) near the n+ side, (ii) in the center, and (iii) near the p+ side of the depletion region. The optical impulse response of these devices consists of a short pulse and a long exponential tail with a bias‐dependent time constant. The relative charge in the fast and slow components could be measured and it was shown that the charge ratios correspond to the fraction of the depletion region transited before and after trapping. These studies show that electron trapping times are much shorter than hole trapping times, and that fast photodetection can occur even in the presence of a severe hole trapping problem if the distance between the trap and the p+ side of the depletion region is much smaller than t...

Significant improvement of electroabsorption saturation intensity by use of AlGaInAs as barriers for GaInAs multiple quantum wells

It is shown that quaternary AlGaInAs is an excellent barrier material for long wavelength modulators using GaInAs quantum wells. Quaternary AlGaInAs has a lower trap density than ternary AlInAs. A low valence-band discontinuity results in saturation intensities at least a factor of 30 higher than those obtained with InP barriers. Decreasing the barrier thickness increases saturation intensities by an additional factor of five.<<ETX>>