Physica Status Solidi A - Applications and Materials Science vol:204 issue:1 pages:152-158
Manganese doped II-IV-V-2 chalcopyrites are promising candidates for room temperature ferromagnetic semiconductors. In this category, we report a new material MgGeAs2: Mn for MBE growth on GaAs substrates. Firstly, we investigated the growth of MgGeAs2 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 Mg3As2 and columnar grains with composition modulation. On GaAs(111)B, we obtained single crystalline films of 35 mn with a smooth surface at an optimized growth temperature of 560 degrees'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 (00 1) and (I I I)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 x 10(17)similar to 3 x 10(18) cm(-3)) in germanium rich samples and p-type conduction (p = 8 x 10(18) similar to 2 x 10(19) cm(-3)) in magnesium rich samples. Two ways of manganese incorporation were tried on (I I l)B grown MgGeAs2: (1) in-situ solid state reaction by annealing a manganese layer deposited on top of MgGeAs2 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.