The desorption of indium during molecular beam epitaxy (MBE) growth of InGaAs and GaAs/InGaAs/GaAs quantum wells has been investigated by reflection high energy electron diffraction (RHEED). The indium desorption activation energy calculated from the temperature dependence of the InAs growth rate is shown to be almost same as the enthalpy of InAs decomposition. It was found that the RHEED pattern transition time, t1, from (4×2) of InGaAs to (2×4) of GaAs after GaAs heteroepitaxial growth on InGaAs began, was the desorption time of indium, which segregated to the growth front from the topmost layer of InGaAs. The activation energy determined from this process is close to the desorption enthalpy of indium from indium liquid.

No abstract

An in-plane gate field-effect transistor is characterized by ultrafast electro-optic sampling. The transistor is monolithically integrated with photoconductive switches in coplanar waveguide and <0.5 ps measurement time resolution is achieved. The gate-drain capacitance of the transistor is obtained as 1.8 fF at zero drain voltage from displacement current transients. The gate-drain capacitance is dominated by parasitic capacitance and the intrinsic gate-drain capacitance is estimated as less than 0.2 fF.

GaAs grown by molecular beam epitaxy (MBE) at 300 °C is annealed at 800 °C and optical properties are studied using photoluminescence spectroscopy (PL) and infrared-absorption spectroscopy. Three kinds of defects are observed. One of them is attributed to gallium vacancies with an energy level at 0.3 eV above the valence-band edge. The concentration of gallium vacancies is increased by the high-temperature annealing. The GaAs can render inactive free electrons of 1.3×1018 cm−3 even after annealing at 800 °C for 10 min.

A process technology for a pseudomorphic high electron mobility transistor (P-HEMT) with an offset-gate structure has been developed for millimeter-wave monolithic microwave ICs (MMICs). A HEMT with the offset-gate structure showed both reduced gate-to-drain capacitance and drain conductance compared with a device with a non-offset-gate structure. The device showed a maximum available gain (MAG) of 9 dB at 77 GHz. The device was applied to a 77 GHz three-stage power amplifier, which showed a small-signal gain of 16.5 dB. Under preliminary life testing, this amplifier showed a stable small-signal gain for over 160 hours of testing at 175°C.