Analysis of buried (Al,Ga)As interfaces after molecular-beam epitaxy overgrowth

Abstract

The buried interface (IF) formed by molecular-beam epitaxy overgrowth on differently prepared (Al,Ga)As templates has been analyzed by secondary ion mass spectrometry and capacitance/voltage profiling. For the regrowth of GaAs on GaAs the lowest IF contamination is achieved by a H-assisted oxide desorption at 450 °C. This process retains atomically flat surfaces and is highly efficient in reducing the carbon contamination and the interfacial carrier depletion compared to thermal oxide desorption at 580 °C. For the regrowth on AlxGa1−xAs templates, due to the high reactivity of Al, the carbon and oxygen contaminations increase with increasing Al-mole fraction. An efficient reduction of the IF contamination can be accomplished by reevaporating a sacrificial GaAs cap layer. Carrier deficits as low as 7×1011 cm−2 for the H-assisted oxide-desorbed GaAs homointerface and 7.5×1011 cm−2 for AlxGa1−xAs on Al0.5Ga0.5As after reevaporating the sacrificial GaAs cap could be achieved. The carrier deficit can be compensated by a tailored doping profile around the IF.