Characteristics of a In/sub 0.52/(Al/sub x/Ga/sub 1-x/)/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As(0/spl les/x/spl les/1) heterojunction and its application on HEMT's

The quaternary In/sub 0.52/(Al/sub x/Ga/sub 1-x/)/sub 0.48/As compound on InP substrates is an important material for use in optoelectronic and microwave devices. We systematically investigated the electrical properties of quaternary In/sub 0.52/(Al/sub x/Ga/sub 1-x/)/sub 0.48/As layers, and found a 10% addition of Ga atoms into the InAlAs layer improves the Schottky diode performance. The energy bandgap (E/sub g/) for the In/sub 0.52/(Al/sub x/Ga/sub 1-x/)/sub 0.48/As layer was (0.806+0.711x) eV, and the associated conduction-band discontinuity (/spl Delta/E/sub c/), in the InAlGaAs/In/sub 0.53/Ga/sub 0.47/As heterojunction, was around (0.68/spl plusmn/0.01)/spl Delta/E/sub g/. Using this high quality In/sub 0.52/(Al/sub 0.9/Ga/sub 0.1/)/sub 0.48/As layer in the Schottky and buffer layers, we obtained quaternary In/sub 0.52/(Al/sub 0.9/Ga/sub 0.1/)/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As HEMTs. This quaternary HEMT revealed excellent dc and microwave characteristics. In comparison with the conventional InAlAs/InGaAs HEMT's, quaternary HEMT's demonstrated improved sidegating and device reliability.