An SCFL (source coupled FET logic) -based ring oscillator was fabricated with pseudomorphic InGaAs channel high electron mobility transistors (HEMTs) with an extrinsic transconductance of 1.96S/mm. A low power consumption of 26.9mW/gate was obtained for the SCFL inverter along with a propagation delay time of 5.08ps/gate. Low-power operation without sacrificing the propagation delay time is possible because of the low knee voltage of less than 0.3V and the high threshold voltage of near zero volts of a HEMT. These results demonstrate the possibility of the large-scale integration of HEMTs using low-power and high-speed circuit configurations.
We experimentally demonstrated a dispersion-tolerant optical short pulse transmission technique using frequency chirp control for the first time. We achieved optical fiber transmission with a dispersion range of -240 to +240ps/nm for 4ps optical RZ pulses.
A low power, 3.3V BiCMOS voltage buffer is presented showing gigahertz operation, low output impedance and low input current. The buffer is designed to make the voltage at an unused negative output of a current switching DAC equal to the voltage of the positive current output, thus increasing the switching speed of the DAC. By consequence the buffer has to sink a fast switching current. A super emitter follower is used for achieving the low output impedance whereas base current compensation is used to reduce the input current. Simulation results in a 0.35µm SiGe BiCMOS process are included demonstrating a low output impedance, a small input current, a high 3dB bandwidth and a good transient response at 330µW static dissipation.
By investigating links between Reed-Muller transform and Walsh-Hadamard spectra an exact and non-exhaustive algorithm for the generation of optimal Reed-Muller expansions directly from just few Walsh-Hadamard spectral coefficients has been developed. The algorithm makes use of the properties of Walsh-Hadamard spectra and by using only few Walsh-Hadamard coefficients the optimal Reed-Muller expansion is obtained for all Boolean functions through the provided equations in the new algorithm.
Fluorine atoms intruded into the channel layer in P-HEMT and degraded its carrier density and electron mobility during the SiO2 RIE process. Thermal annealing at 300°C for 10 minutes was rather effective for recovering from this plasma damage. Our SIMS investigation revealed that the mechanism of this recovery was the removal of fluorine atoms from the channel layer and their accumulation in the δ-doped Si layer. Ionized impurities in the channel layer were removed, and electron mobility was significantly recovered. However, the carrier density was recovered to a lesser degree than that of the electron mobility because of the neutralization of Si donors in the δ-doped layer caused by the fluorine accumulation.