G. Janssen

Development of a low-impedance traveling wave amplifier based on InAlAs/InGaAs/InP-HFET for 20 Gb/s optoelectronic receivers

The applicability of the transimpedance amplifier for optoelectronic receivers becomes doubtful for bit rates higher than 20 Gb/s. So recently the traveling wave amplifier (TWA) concept for high bit rate receiver systems is of increasing interest because it is the preferred amplifier concept for broadband applications like hierarchically organized communication interlinks. TWAs usually are designed with an input and output impedance of 50 /spl Omega/. Thus a main problem of the TWA-concept for an optoelectronic receiver is matching the photo-detector (PD) and the TWA input and reach the requested input RC-bandwidth. The conventional approach is a TWA with an additional 50 /spl Omega/ match resistor at the input line, which has to be integrated directly into the PD itself in order to avoid parasitics. The aim of this paper is to present an alternative concept to the match resistor realized by a TWA with a low-impedance input (25 /spl Omega/), which yields significantly reduced design and fabrication efforts. All simulations for the investigated and optimized designs of the TWA in coplanar technique have been carried out using a commercially available software. For exact noise and sensitivity simulations, an extended temperature noise model (TNM) for heterostructure field-effect transistors was developed and implemented. Finally a comparison with measurement results of the realized TWA is presented.

A novel 3-D integrated RTD-HFET frequency multiplier

A frequency multiplier circuit using a resonant tunneling diode (RTD) as a load of a HFET is developed. Based on 3D-monolithic integration on a semi-insulating InP-substrate, a demonstrator is realised generating odd higher harmonics with high efficiency. The multiplier is highly compact and combines amplification of the fundamental frequency in the HFET with the high switching performance of the RTD. The Microwave Design System is used to evaluate its ultra high frequency potential predicting 0.115 times the voltage amplitude of the fundamental input signal for the third harmonic at 100 GHz. Optimization of the circuit design and the RTD-layer structure on top of the HFET with respect to the peak and valley parameters will increase the efficiency.

27 GHz bandwidth integrated photoreceiver comprising a waveguide fed photodiode and a GaInAs/AlInAs-HEMT based travelling wave amplifier

Optical front-ends are considered to play a major role in future communication systems operating at bit rates of 20 or even 40 Gbit/s, as well as in mobile communication systems with fibre-optic distribution networks. Consequently, different approaches for the monolithic integration of high-speed receivers for a wavelength of 1.55 /spl mu/m can be found in the literature. In this paper, we report on the first monolithical integration of an optical receiver OEIC, which combines the advantageous high-speed characteristics of the waveguide integrated pin photodiode and of the travelling wave amplifier (TWA) circuit, both based on the InP material system.

On the applicability of the transimpedance amplifier concept for 40 Gb/s optoelectronic receivers based on InAlAs/InGaAs heterostructure field effect transistors

We examine the design considerations and include a general discussion of the applicability of the transimpedance amplifier concept for optoelectronic receivers at extremely high bit rates up to 40 Gb/s. The receiver design is based on a low gate-leakage InAlAs-InGaAs-InP heterostructure field effect transistor (HFET). The noise modeling of these devices is done using an extended temperature noise model in order to produce a reliable extrapolation far beyond the frequency limits of common measurement setups. The fitted transistor model shows excellent agreement with measured data concerning RF as well as the noise performance. The evidence of inductive peaking near the corner frequency of the transimpedance Z_/sub T/ is correlated to a phase difference between the voltage gain V_/sub u/ and Z_/sub T/ itself. Furthermore, the distinct influence of the length of the feedback line on the receiver performance is discussed. Based on 0.7 /spl mu/m gate HFETs produced by optical lithography and offering a current gain cut off frequency of f/sub T/=40 GHz the following receiver features can be predicted: low frequency transimpedance Z_/sub T0/=39.4 dB/spl Omega/, corner frequency f/sub 3dB/=22 GHz, mean equivalent input noise current density i~/sub na//spl ap/43 pA//spl radic/Hz. Thus the receiver shows an excellent calculated sensitivity of /spl eta/P/sub min/=-13.2 dBm at 40 Gb/s.

10 Gb/s low-noise transimpedance amplifier for optoelectronic receivers based on InAlAs/InGaAs/InP HEMTs

A transimpedance amplifier based on 0.7 /spl mu/m InAlAs/InGaAs/InP HEMTs and applicable for bit rates in the range of 2.5-10 Gb/s has been developed and realized. Compact chip layout guarantees extremely flat gain, linear phase and very small group delay time variations, respectively. Measured transimpedance is Z/sub TO/=51.6 dB/spl Omega/ (f/sub 3/ /sub dB/=8.5 GHz) for the 10 Gb/s version. Mean equivalent input noise current density is i/sub na/=7.98 pA//spl radic/(Hz) over the bandwidth 0/spl les/f/spl les/10 GHz. Calculated receiver sensitivity is /spl eta/P/sub min/=-24.1 dBm@10 Gb/s and BER=10/sup -9/.

Quantitative X-ray analysis of high performance InP/(InGa)As:C HBT for rapid non-destructive material qualification

Carbon doped InP/(InGa)As Heterostructure Bipolar Transistors (HBT) are of interest for todays (OC-768) and tomorrows (OC-3072, 100 Gbit Ethernet, UMTS) communication standards. For a reliable fabrication of these complex radio frequency (opto-)electronic circuits, a quantitative InP process technology control is necessary starting at the level of device epi-layer stacks. In this paper the quantitative characterization of an InP/(InGa)As:C HBT is carried out by non-destructive X-ray analysis. Based on X-ray measurements in 004- and 002-reflection, a detailed analysis of complex device layer stacks is purposed. As a result, an automatic calculation of layer parameters, e.g. thickness and composition is possible, reducing the turnaround time for statistical process control (SPC).

An intrinsically coupled HBT/RTD device enabling an adjustable peak-current-density

For the two terminal Resonant-Tunneling-Diode (RTD) the device functionality is dominated by the epitaxially grown layer sequence consisting of very thin layers, i.e. a variation of the barrier layer thickness shows an exponential impact on the RTD peak-current density. This is a major drawback for the use of RTD devices for circuit applications and has to be compensated by novel circuit architectures like the MOnostable BIstable Logic Element (MOBILE). The operation principle of a MOBILE is based on the comparison of the absolute RTD peak-current scaled by the RTD device area. By this method the exponential impact of epitaxial growth variations are reduced to less critical lateral scaling rules. But the design of programmable and/or multiple-valued logic functions is inhibited because the current is defined by the RTD area, only. In this work a novel HBT/RTD device is presented with a controllable peak-current density S/sub Peak/. The proposed intrinsically coupled HBT/RTD device enables a direct adjustment of the peak-current-density by the B/E input voltage and simplifies the MOBILE circuit topology. The RTD layer sequence is integrated inside the collector of the HBT directly at the B/C junction. By this way the charge accumulation n/sub BC/ at the RTD structure can be controlled by the bipolar effect which results in an intrinsically coupled device structure (n/sub BC/=f(V/sub BE/). The applicability of the RTD/HBT device combinations to circuit concepts based on programmable MOBILE threshold and Boolean gates and multiple-valued-logic is discussed. For multiple-valued-logic applications and programmable XNOR, XOR, NAND, NOR logic gates the achieved low RTD peak-voltages are of major importance while enabling level compatibility.