Properties and applications of Al xGa 1−xAs (0 ≤ χ ≤1) grown at low temperatures

Abstract

We have used low temperature MBE growth to obtain highly resistive GaAs and AlGaAs layers with potential applications in a variety of devices. Using MIS structures, we have examined the resistivity of AlGaAs for various aluminum mole fractions and growth temperatures. A GaAs resistor structure was grown at 300°C and a resistivity of 5 × 10 5 Ω cm is measured. This agrees well with the resistivity of 3 × 10 5 Ω cm measured using an MIS structure. Furthermore, we have grown a HEMT structure with high mobility ( μ = 156,000 cm 2 V −1 s −1 at 77 K) and electron sheet density ( n s = 6.0 × 10 11 cm −2 at 77 K) on a highly resistive low-temperature grown (LTG) Al 0.3Ga 0.7As/GaAs superlattice buffer. To test the LTG AlGaAs as possible dielectric for microwave applications, a coplanar waveguide (CPW) was fabricated on a 0.75 μm epitaxial Al 0.3Ga 0.7As layer grown at 270°C. There was virtually no difference in the measured S-parameters for the coplanar waveguide (CPW) fabricated on the 0.75 μm epitaxial Al 0.3Ga 0.7As layer and the CPW made directly on a semi-insulating GaAs wafer.