J. Hilsenbeck

Low phase noise MMIC VCOs for Ka-band applications with improved GaInP/GaAs-HBT technology

We report on the technology and performance of fully monolithic coplanar voltage-controlled oscillators (VCOs) with GaInP/GaAs-HBTs as the active devices. With our optimized HBT process, the parasitic base resistance R/sub B/ and extrinsic base-collector capacitance C/sub EX/ are significantly reduced. In this way, the maximum frequency of oscillation F/sub max/ is increased from 100 to 170 GHz. This allows us to realize fundamental 38 GHz-VCOs with very low phase noise. At an oscillation frequency F/sub res/=34.2/spl plusmn/0.2 GHz, the VCO reaches phase noise levels of -87 dBc/Hz @ 100 kHz and -108 dBc/Hz @ 1 MHz offset frequency, respectively. To our knowledge, these phase noise values are the lowest GaAs data for Ka-band applications reported so far.

Low phase-noise GaInP/GaAs-HBT MMIC oscillators up to 36 GHz

Monolithic coplanar 18 and 36 GHz oscillators with GaInP/GaAs-HBTs and on-chip resonators are presented. Measured phase-noise reaches -93 dBc/Hz and -91 dBc/Hz at 100 kHz offset for 18 and 36 GHz, respectively. These values demonstrate that GaAs-HBT oscillators yield a phase-noise performance comparable to SiGe-HBTs, with the potential for higher frequencies.

38 GHz push-push GaAs-HBT MMIC oscillator

Two differential coplanar MMIC HBT oscillators are presented, a fixed frequency and a VCO version. They provide single-ended output at the second harmonic at 38 GHz as well as differential output at 19 GHz. The oscillators show excellent phase noise performance, the fixed-frequency type reaches -95 dBc/Hz at the fundamental frequency and -89 dBc/Hz at the second harmonic, at 100 kHz offset.

Reliability considerations of III-nitride microelectronic devices

Abstract The success of III-nitride optoelectronic devices paths the way towards emerging devices in microelectronics. These devices are currently at the threshold to commercialization, therefore reliability considerations are becoming increasingly important. This paper reviews the material and process technology of III-nitride microelectronic devices in the scope of reliability. Since statistical reliability data are lacking in the current state of research the review starts with a summary of how reliability can be designed into process modules being relevant for microelectronic devices. This includes a discussion of the most important issues of material growth, metallization, implantation, dry etching and surface passivation. The subsequent chapter focuses to microelectronic devices and highlights technological challenges that have to be met in order to obtain reliable devices. Finally, results of lifetime experiments (thermal aging) demonstrate that III-nitride devices have the potential for reliable operation even at elevated temperatures up to 400°C.

Reliability of AIGaN/GaN HFETs comprising refractory ohmic and Schottky contacts

Abstract Recent progress in the development of AlGaN/GaN heterostructure field effect transistors (HFETs) shows the great potential towards high temperature / high power electronics. Nevertheless investigations on reliability properties of GaN-based devices are still at the beginning. The frequently used Ti/Al based ohmic and Pt based Schottky contacts suffer from strong degradation after aging at elevated temperatures. Therefore new contact systems have to be employed. Concerning the source and drain metallization we used an amorphous WSiN barrier layer as applied for GaAs on top of the Ti/Al-based ohmic contact. This technique significantly reduces the in-diffusion of the Au-containing overlayer, furthermore the barrier layer guaranties smooth contact morphology after RTA and aging, respectively. For the Schottky metallization the Ir/Au system was used. Reliability studies performed on I-IFET devices containing refractory Ti/Al/Ti/Au/WSiN ohmic and Ir/Au Schottky contacts demonstrate stable conditions during 120h aging at 500°C.

A 40 Gbps broadband amplifler for modulator- driver applications using a GaAs HBT technology

A broadband amplifier suitable for high-bitrate modulator driver applications is fabricated using a GaAs-HBT process with f r and fmu of 45 and I 7 0 GHr, respectively. The design takes optimum advantage of the available technology, to obtain a broadband gain of 12 dB and a 3dB cut-off-frequency of 24 GHL A smooth decrease around f c is chosen in order to keep a positive gain value at higher frequencies and a relatively frat group delay, which is a key condition for the eye-diagram opening. This appears to be the best way to combine high bitrate signal amplification with sujj7ciently high output voltage for a relatively low f r HBT technology, compared to others, as InP HEMT or GaAs pHEMT. According to the NRZ power spectra, 40 Gb/s signal amplification is possible with such characteristics since the smooth slope condition is fulfilled. Eye diagram measurements at 40 Gb/s with several input signal swings are presented A 4 Vpp output well-opened 40 Gb/s eye diagram is obtained with a large signalgain of 12 dB. This is a promising resuit for 40 Gb/s modulator driver applications using low-cost standard technologies and an interesting perfomiance in terms of a marimurn broadband5 to (f7, fnp3 ratio.

XTEM and TFXRD investigations of ohmic Ti/Al/Ti/Au/WSiN contacts on AlGaN/GaN HFET layer systems

The microstructural features of the high-temperature-stable ohmic contact system Ti/Al/Ti/Au/WSiN on AlGaN/GaN were investigated using analytical transmission electron microscopy and thin film x-ray diffraction. For two typical rapid thermal annealing steps at 750 °C (non-ohmic behaviour) and 850 °C (ohmic behaviour) the intermetallic phases at the metal-semiconductor interface are presented. Increased annealing leads to the transformation of an Al2Au-AlAuTi phase mixture to a mixture of Al2Au-Al3Au8 phases and the formation of Ti-Al-nitride layers at the interfaces. In light of these results the electrical contact properties are discussed.

Integrated Circuits and 3D-Packaging for Low-Power 24 GHz Front End

ByChafikMeliani, ProdyutTalukder, Jochen Hilsenbeck, Meik Huber, Georg Bock, and Wolfgang Heinrich Abstract Design and experimental results for a low-power monolithic 24 GHz front end are described. As basic circuits, VCO and mixer are presented. The circuits are realized on GaAs using heterobipolar transistors. The VCO reaches 19% efficiency at 4.3 dBm output power and 14.5 mW DC power consumption. The circuits are to be integrated together with a special slot antenna using flip-chip technology. Simulatbn data on this novel antenna approach demonstrate acceptable gain characteristics around 3 dB, despite of its small size.

Uniformity and Scalability of AlGaN/GaN HEMTs Using Stepper Lithography

AlGaN/GaN HEMTs processed by 2 inch stepper lithography in a production line environment are presented. The uniformity of the HEMTs is assessed, showing an excellent homogeneity of electrical properties over the wafer. Typical values for maximum saturation current, transconductance and pinch-off voltage are: 616 mA/mm, 203 mS/mm, -3.5 V with very good homogeneity across 2. The cut off frequencies F T and F max are 23 and 57 GHz, respectively. Standard deviations across the wafer for the dc properties are below 3%.