New aluminium precursors for MOMBE (CBE): a comparative study

Recently different new Al precursors have been developed to improve the electrical and optical quality of AlGaAs layers grown by MOMBE (CBE), since AlGaAs layers still suffer from the high incorporation of oxygen and carbon. Three approaches are introduced and results obtained from Al_xGa_1?xAs layers (0 < x ≤ 1) are discussed. APAH, a double ring structure molecule, was found to yield AlGaAs layers with high contents of carbon and nitrogen. The use of an Alane-adduct decreases impurity concentrations and improves optical properties. However, TIBAl is superior and provides highest PL response together with carrier concentrations below p = 10¹⁶ cm^-3. Even though the concept of coordinative saturation is promising, results achieved by TIBAl showed that trialkyls could also be well suited for AlGaAs, assuming that they are properly synthesized.