Germanium as a deep level in alxga1− xas grown by organometallic vapor phase epitaxy

Abstract

Optoelectronic devices require materials which exhibit extremely low trap concentrations. The AlxGa1−xAs system has been used extensively for optoelectronic applications despite trap concentrations in the AlxGa1−xAs which limit the efficiency of the resulting devices. Deep level transient spectroscopy (DLTS) performed on Al0.2Ga0.8As layers grown by organometallic vapor phase epitaxy (OMVPE) has revealed three traps with concentrations >1013 cm−3 -Ec-Et = 0.3, 0.5 and 0.7 eV. The dominant source of the 0.3 eV trap has proven to be a Ge impurity in arsine. SIMS analysis of Al0.2Ga0.8As samples show Ge as the only candidate for the impurity responsible for the 0.3 eV trap. DLTS and SIMS analysis performed on Al0.2Ga0.8As samples intentionally doped with Ge displayed a proportional increase in the 0.3 eV trap concentration with the Ge concentration and establishes that Ge is indeed the source of the 0.3 eV trap in AlxGa1−xAs. Comparison of C-V, SIMS and DLTS measurements performed on AlxGa1-xAs:Ge indicate that approximately 30% of elemental Ge incorporated created the 0.3 eV trap, DXGe.