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During the past five years numerous mixed signal integrated circuits (IC's) have been designed, processed, and characterized based on our 0.2 mu m gate length AlGaAs/GaAs quantum well HEMT technology. Utilizing the inherent advantages of the AlGaAs/GaAs material system, optical, analog, microwave, and digital functions have been integrated monolithically. Examples are a chip set for 40 Gb/s optoelectronic data transmission systems, 15 and 34 GHz PLL's, a 35 GHz phase shifter for phased array antenna applications, a 2-kb ROM with subnanosecond access time for direct digital signal synthesis, and a 6-k gate array

We report about a systematic study on the influence of the barrier thickness (LB) and the spacer length (Ls) on the current/voltage behavior of AlAs/GaAs/AlAs resonant tunneling diodes (RTDs) to achieve a high peak current density up) and a low valley current density (iv) for device applications at room temperature. The samples are grown by molecular beam epitaxy. With increasing LB in the range between 3 monolayers (ML) and 6 ML we observe a drastic increase of the peak-to-valley current ratio (PVR = jp'jv) up to a maximum value of 5 (12) at 300 K (77 K) for LB = 6 ML, Simultaneously, j, decreases exponentially with thicker barriers. A maximum available current density in the negative-differential-resistance region of Aj = jp -j, = 165 W c m 2 at 300 K is achieved for 4ML thick AlAs barriers. We found no remarkable influence of the emitter spacer length variation on jp for L, > 10 nm. However, for Ls < 10 nm jp increases with decreasing Ls (maximum improvement of 60 $6 for Ls = 0.5 nm). The PVR can be significantly improved by using a pseudomorphic InGaAs prewell (PW) layer for carrier injection. We observe PVR values of 7.2 at 300K and 27 at 77K. Additionally, jp increases by a factor of 6 in comparison with standard samples without a PW layer. By incorporation of an AlGaAs prebarrier layer we also obtain an improvement of PVR, but the peak current density is reduced. High frequency operation of RTDs is investigated in a waveguide resonator.

AbstractÀModern active electronically steered antennas (AESA) operate in different platforms and systems. Inside EADS/ CASSIDIAN, the focus on X-band antennas today is on airborne and fighter nose radars, in satellite based SAR antennas (synthetic aperture radar) for earth observation, and ground surveillance and security radars.Active antennas are assembled with hundreds or even thousands of transmit/receive modules. This paper will describe an example of a so-called standardized module solution based on LTCC package technology. State-of-the-art modules are assembled with active components such as MMICs realized in GaAs technology, for example, the low noise amplifier (LNA) and the high power amplifier (HPA), silicon based devices, and passives. Assembly technologies are optimized for high yield series production inside CASSIDIAN MicroWave Factory. New semiconductor technologies, such as GaN (gallium nitride) are enablers for a new transmit/receive module generation. GaN/SiC based MMICs with higher power density compared with GaAs-based devices are technological challenges for innovative thermal management solutions and assembly alternatives. GaN power devices are soldered on modern heat sink materials with high thermal conductivity and matched CTE (between the MMIC and the heat sink).The results of thermal simulations comparing different heat sink materials in combination with soldering techniques will be discussed and an optimized solution will be shown. Another type of transmit/receive module technology based on RF-PCB and packaged MMICs will be discussed. Future applications of ground-based security radars, active antenna products with a one-dimensional array, and the need for cost-effective solutions seem to be a good fit for SMD-based products. Different packages, for example, QFN (quad flat pack no lead) and ceramic based (HTCC), mainly for power devices will be shown and compared.

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