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We report performance of sub-0.25pm emitter-width InPflnGaAsilnP DHBTs. These are the smallest emitterwidth Ill-V devices reported to date. Measured ft'fmax performance of 406GHd423GHz is the first ever reported for a sub-0.25pm emitter-width DHBT and among the fastest for any DHBTs. With the peakf; and fmw. performance occurring at I, = 8mA (Vch-1.2Sv), this is the lowest power consumption DHBT ever reported with state of the art cutoff frequencies. The as-patterned emitter contact metal width for these devices was 0.25pm and the width of the emitter at the emitter-base junction is less than 0.25pm owing to undercutting of the underlying emitter semiconductor. When comparing with 0.4pm emitter width DHBTs, we find that 0.4pm device has the higher measured f,, 4 2 0 G H z , due to the lower emitter resistance for that emitter layout. Fmsx was highest for the 0.2Spm emitter devices due to lower hasecollector mesa capacitance, Ca, which results from the reduced mesa width. We find this behavior to be consistent with scaling tradeoffs in the design of ultra-fast DHBTs.

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The Primary Mirror of the Keck Observatory Telescope is made up of an array of 36 hexagonal mirror segments underactive control. The measurement of the relative orientations of the mirror segments is fundamental to their control. The mechanical and electronic design of the sensors used to measure these relative positions is described along with the performance of the sensors under a variety of tests. In use, the sensors will measure relative positions with a resolution of a few nanometers. This resolution and the low noise, drift and thermal sensitivity of the sensors are adequate to stabilize the primary mirror figure to the precision required for optical and infrared astronomy.

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The potential for InAs-based heterojunction bipolar transistors (HBTs) to be used for high speed, low power applications has been demonstrated.[l] The material properties that give InAs an advantage over InGaAs-based HBTs include a low bandgap, low electron effective mass, high peak velocity and high electron mobility. However, a new technology presents new challenges for process development engineers. In this talk, InAs-based HBT technology will be discussed. Several of the available fabrication processes will be presented as well as the device performance obtained from some of these options.The first major difference between InAs technology and other In-V HBT technologies is the

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