PROPERTIES AND APPLICATIONS OF ALXGA1-XAS (0 LESS-THAN-OR-EQUAL-TO X LESS-THAN-OR-EQUAL-TO 1) GROWN AT LOW-TEMPERATURES

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-degrees-C and a resistivity of 5 x 10(5)-OMEGA-cm is measured. This agrees well with the resistivity of 3 x 10(5)-OMEGA-cm measured using an MIS structure. Furthermore, we have grown a HEMT structure with high mobility (mu = 156,000 cm2 V-1 s-1 at 77 K) and electron sheet density (n(s) = 6.0 x 10(11) cm-2 at 77 K) on a highly resistive low-temperature grown (LTG) Al0.3Ga0.7As/GaAs superlattice buffer. To test the LTG AlGaAs as a possible dielectric for microwave applications, a coplanar waveguide (CPW) was fabricated on a 0.75-mu-m epitaxial Al0.3Ga0.7As layer grown at 270-degrees-C. There was virtually no difference in the measured S-parameters for the coplanar waveguide (CPW) fabricated on the 0.75-mu-m epitaxial Al0.3Ga0.7As layer and the CPW made directly on a semi-insulating GaAs wafer.