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-μm-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°C. The substrate temperature was raised to 580°C for a brief in situ anneal and followed by the growth of the active spike-doped GaAs MESFET structure. The peak extrinsic transconductance, gm, was 600 mS/mm with an average pinch-off voltage, Vpo, of -0.6 V. An output conductance, go, of 24 mS/mm resulted in a voltage gain of 25. The extrapolated fT 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°C, followed by an anneal under arsenic overpressure and a GaInAs/AlInAs superlattice prior to the HEMT structure, which is grown at T$-$/ = 510°C. Devices fabricated with 0.2-μm gates had gm of 670 mS/mm and go of 2.55 mS/mm, giving a voltage gain of 250.
