GERMANIUM AS A DEEP LEVEL IN ALXGA1-XAS GROWN BY ORGANOMETALLIC VAPOR-PHASE EPITAXY

Optoelectronic devices require materials which exhibit extremely low trap concentrations. The Al(x)Ga1-xAs system has been used extensively for optoelectronic applications despite trap concentrations in the Al(x)Ga1-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 > 10(13) cm-3 - E(c)-E(t) = 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 Al(x)Ga1-xAs. Comparison of C-V, SIMS and DLTS measurements performed on Al(x)Ga1-xAs:Ge indicate that approximately 30% of elemental Ge incorporated created the 0.3 eV trap, DX(Ge).