Electrical properties of InAlAs/InGaAs HEMT structures on InP substrates under the optimum thermal cleaning condition grown by MBE

To optimize the thermal cleaning condition of InP substrate for growth of molecular beam epitaxy (MBE), the thermal cleaning temperature dependence of the electrical properties of the epitaxial layer and of the impurity concentration in the epi-substrate interface was investigated. It was revealed that, at low cleaning temperatures, the sheet carrier concentration of epitaxial layers was proportional to the oxygen concentration in the interface and the main residual impurity in the interface was oxygen. At high cleaning temperatures, a deterioration of the surface morphology and the electron mobility of epitaxial layers was observed. The optimum thermal cleaning temperature was determined to be around 550 degrees C. The effects of the structural parameters on the electrical properties of the In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As HEMT (high electron mobility transistor) structure were also investigated. A maximum electron mobility of 65900 cm12/Vs with a sheet carrier concentration of 1.1*10/sup 12/ cm/sup -2/ at 77 K was obtained with a spacer layer thickness of 20 nm.<>