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Tetsuya SUEMITSU Tetsuyoshi ISHII Yasunobu ISHII
InP-based high electron mobility transistors (HEMTs) with gate lengths reduced to 30 nm were fabricated and characterized, and the effect of the gate recess on the high-frequency characteristics was studied. The cutoff frequency, which is regarded as a function of the gate length and the average carrier velocity in a first-order approximation, depends on the size of the gate recess when the gate length becomes short. The size of the gate recess is optimized by taking the feed-back capacitance and the parasitic resistance into account. For HEMTs having the gate recess with an InP surface, an appropriate widening of the gate recess gives a record cutoff frequency of 368 GHz for the 30-nm-gate HEMTs with a lattice-matched channel.
Jun MIYAZU Toru SEGAWA Shinji MATSUO Tetsuyoshi ISHII Hiroyuki SUZUKI Yuzo YOSHIKUNI
Apodised chirped gratings based on InGaAsP/InP deep-ridge waveguides with vertical-groove surface gratings were fabricated. Reflectivity ripple and group delay ripple were reduced from around 4 dB to 1 dB and from around 5 ps to 2 ps, respectively, by apodisation over a wavelength range of around 20 nm.