Low temperature MBE growth of GaAs and AlInAs for high speed devices

Low-temperature GaAs buffer technology was used to fabricate high-performance 0.2- mu m-gate-length, spike-doped GaAs MESFETs. A 400.0-nm low-temperature GaAs buffer was grown by molecular beam epitaxy (MBE) at a substrate temperature of 300 degrees C. The substrate temperature was raised to 580 degrees C for a brief in situ anneal and followed by the growth of the active spike-doped GaAs MESFET structure. The peak extrinsic transconductance, g/sub m/, was 600 mS/mm with an average pinch-off voltage, V/sub po/, of -0.6 V. An output conductance, g/sub o/, of 24 mS/mm resulted in a voltage gain of 25. The extrapolated f/sub T/ of the devices was 79 GHz. Static SCFL (source-coupled FET logic) frequency dividers fabricated in this technology exhibit a maximum clock rate of 22 GHz. Low-temperature AlInAs buffer growth has been applied to GaInAs/AlInAs HEMT (high-electron-mobility transistor) devices on InP. A 250.0-nm AlInAs buffer was grown at a substrate temperature of 150 degrees C, followed by an anneal under arsenic overpressure and a GaInAs/AlInAs superlattice prior to the HEMT structure, which is grown at T=510 degrees C. Devices fabricated with 0.2- mu m gates had g/sub m/ of 670 mS/mm and g/sub o/ of 2.55 mS/mm, giving a voltage gain of 250.<
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