MBE growth of MgGeAs 2 :Mn on GaAs substrate

Manganese doped II–IV–V 2 chalcopyrites are promising candidates for room temperature ferromagnetic semiconductors. In this category, we report a new material MgGeAs 2 :Mn for MBE growth on GaAs substrates. Firstly, we investigated the growth of MgGeAs 2 on GaAs (001) and (111)B. Stoichiometric growth conditions were established with assistance of XPS measurements. On GaAs (001), RHEED, XRD and TEM revealed phase separation with the formation of Mg 3 As 2 and columnar grains with composition modulation. On GaAs(111)B, we obtained single crystalline films of 35 nm with a smooth surface at an optimized growth temperature of 560 °C and a beam equivalent pressure ratio Mg:Ge:As = 1:3.1:800. The lattice constant of the chalcopyrite phase is nearly matched to GaAs for both (001) and (111)B growth, in contrast to the theoretical prediction of a 6.1% mismatch. With flux variations of ±10%, Hall measurements at room temperature showed n‐type conduction ( n = 4 × 10 17 ∼ 3 × 10 18 cm –3 ) in germanium rich samples and p‐type conduction ( p = 8 × 10 18 ∼ 2 × 10 19 cm –3 ) in magnesium rich samples. Two ways of manganese incorporation were tried on (111)B grown MgGeAs 2 : (1) in‐situ solid state reaction by annealing a manganese layer deposited on top of MgGeAs 2 and (2) co‐evaporation of manganese during the host material growth. Using method (2), manganese was incorporated by replacing 20% of magnesium without structural change. RHEED and XRD did not reveal the existence of additional phases. However, the preliminary magnetization and transport measurement didn't reveal a ferromagnetic signal in these samples. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)