High-breakdown-voltage Ga/sub 0.51/In/sub 0.49/P channel MESFET's grown by GSMBE
The first Ga/sub 0.51/In/sub 0.49/P channel MESFETs grown on a (100) GaAs substrate by GSMBE have been fabricated. A high gate-to-drain breakdown voltage of 42 V with a high maximum current density (320 mA/mm) was achieved. This result demonstrates that high-breakdown voltage could be attained by using Ga/sub 0.51/In/sub 0.49/P as the channel material. We also measured a high-maximum oscillation frequency (f/sub max/) of 30 GHz for a 1.5 /spl mu/m gate-length device. This value is quite high compared with other high-breakdown-voltage GaAs MESFET's or MISFET's with the same gate length.
High-Linearity High-Current-Drivability Gao.5 1 Ino.49P/GaAs MISFET Using Gao.5 1 Ino.49P Airbridge Gate Structure Grown by GSMBE
A novel structure Gao.51 Im.rsP/GaAs MISFET with an undoped Gao.slIno.*eP layer serving as the airbridge between active region and gate pad was first designed and fabricated. Wide and flat characteristics of gm and f max versus drain current or gate voltage were achieved. The device also showed a very high maximum current density (610 mA/mm) and a very high gate-to-drain breakdown voltage (25 V). Parasitic capacitances and leakage currents were minimized by the air- bridge gate structure and thus high f~ of 22 GHz and high f,,, of 40 GHz for 1 pm gate length devices were attained. To our knowledge, both were the best reported values for 1 pm gate GaAs channel FET's.
Microwave power GaAs MISFET's with undoped AlGaAs as an insulator
A metal-insulator-semiconductor field-effect transistor using an undoped AlGaAs layer as an insulator has been fabricated and RF tested. Due to the higher breakdown field of the wide-band-gap AlGaAs, the gate breakdown voltage has been greatly improved as compared with a conventional GaAs MESFET. The prebreakdown gate leakage current of this new device structure is also much lower than that of the MESFET. The presence of the gate insulator also reduces the gate capacitance. All these factors result in a GaAs power FET structure with potentials for high power, efficiency, and frequency of operation. An unoptimized 750-µm gate-width device achieved an output power of 630 mW with 7-dB gain and 37-percent power-added efficiency at 10 GHz. At reduced output power levels, power-added efficiency as high as 46-percent was obtained at X-band.