Takuji Sonoda

Donor passivation in n-AlInAs layers by fluorine

The origin and mechanism for the thermal degradation of the n-AlInAs layer are discussed. The thermal degradation of carrier concentration and mobility is found to occur predominantly in the n-AlInAs layer, which is caused by annealing at a temperature less than 450/spl deg/C. The origin of the deterioration is ascertained to be the thermally diffused fluorine, which passivates donors in the n-AlInAs layer. As the electronegativity of the fluorine atom is the largest among the elements, and the atomic radius of fluorine atom is considerably small enough to pass through the crystal, fluorine atoms are reasonably thought to diffuse into the n-AlInAs layer then react with the free electrons, which results in the F/sup -/ scattering centers (F/sup -/: ionized fluorine).

A super low noise AlInAs/InGaAs HEMT processed by selective wet gate recess etching

A 0.15 /spl mu/m T-shaped gate AlInAs/InGaAs high electron mobility transistor (HEMT) with excellent RF performance has been developed using a selective wet gate recess etching. The etching condition for recess formation is optimized and an extremely low minimum noise figure (F/sub min/) of 0.9 dB with an associated gain (G/sub a/) of 7.0 dB has been achieved at 60 GHz for a SiON-passivated device.

Three-dimensional modeling of thermal flow in multi-finger high power HBTs

Three-dimensional modeling of thermal flow in multi-finger HBTs has been investigated with thermal network method to find out the optimal structure which can effectively reduce the junction temperature uniformly in whole fingers under the high power operation. Thermal cross-talk effects and temperature distribution in a finger or between the fingers are examined. The HBT structure with emitter air-bridge connected to via hole is proposed as an optimal structure. The estimation accuracy of the calculation was confirmed from the good agreement between the calculation result and the measured value of the thermal resistance in HBT with the emitter air-bridge structure.<<ETX>>

New pseudomorphic N/sup -//N/sup +/ GaAs/InGaAs/GaAs power HEMT with high breakdown voltages

A pseudomorphic N/sup -//N/sup +/GaAs/InGaAs/GaAs power HEMT (high electron mobility transistor) with high breakdown voltages (VB) of more than 20 V and full channel current of 460 mA/mm is described. This power HEMT allows the simultaneous improvement of output power (P/sub out/), linear gain (G/sub L/), and power-added efficiency (N/sub add/) over GaAs FETs. A record maximum output power of 4.7 W at 14.25 GHz was achieved by a large 10.5-mm-wide HEMT chip with G/sub L/ of 8 dB and N/sub add/ of 25%.<<ETX>>

Reliability of Super Low Noise HEMTs

The first report on a comprehensive study of the reliability of super low noise HEMTs with a typical noise figure of 1.2 dB at 12GHz is presented. No failure was observed in both DC running and high temperature storage tests during 2000 hours. These successful results were achieved by a newly developed low temperature ohmic sintering technology and a novel Ni/Al gate.

70% high efficient C-band 27 W hetero-structure FET for space application

A highly reliable and 70% highly efficient C-band 27 W internally-matched GaAs FET with a total gate width of 18.9 mm /spl times/ 4 has been developed for space applications. The newly developed Hetero-structure FET (HFET) successfully reduces the gate leakage current even for RF overdrive region, which is indispensable to improve the power-added efficiency and reliability, simultaneously. The bias conditions and the 2/sup nd/ harmonic tuning for both the input and output matching circuits are also optimized to increase high efficiency. No failure in reliability tests was observed under RF operation based on the European Space Agency Specification (ESA) and RF overdrive at 5dB compression. These excellent results promise that the newly developed HFET can replace the conventional traveling-wave tube amplifiers (TWTAs) for space applications.

A 6 Watt Power GaAs FET for 14.0-14.5GHz Band

An internally matched GaAs FET with output power above 38dBm(6.3W) and linear power gain above 5.8dB has been developed for the 14.0-14.5GHz band. These results were achieved by using high quality GaAs wafers prepared by molecular beam epitaxy (MBE) and optimizing the channel recess structure. Additionally, the package size of the FET was successfully reduced by using a high dielectric substrate for the internal matching circuits of both input and output .

High resistive undoped Al/sub 0.48/In/sub 0.52/As layers grown by MOCVD

It is shown that the resistivity and the conduction type of undoped MOCVD Al/sub 0.48/In/sub 0.52/As layers depend strongly on the growth temperature (450/spl deg/C-650/spl deg/C). The conduction type changes from n-type, semi-insulating and p-type with the decrease of the growth temperature. High resistivity over 2/spl times/10/sup 8/ /spl Omega/-cm is successfully obtained from undoped Al/sub 0.48/In/sub 0.52/As layers grown at 500/spl deg/C. With help of SIMS and ICTS, it is found that the resistivity is substantially determined by the incorporation of carbon whose incorporation rate depends strongly on the growth temperature. The incorporated carbon compensates the native deep donors. The good selective growth of undoped Al/sub 0.48/In/sub 0.52/As layers is also achieved at even low growth temperature of 500/spl deg/C.<<ETX>>