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MBE growth of Mn doped MgGeAs2 on GaAs (0 0 1) and (1 1 1)B

Zhen Li 1,2Mathieu Malfait 3Victor V. Moshchalkov 3Gustaaf Borghs 1Willem Van Roy 1

1. IMEC, Kapeldreef 75, Leuven B-3001, Belgium
2. Katholieke Universiteit Leuven, ESAT-INSYS, Kasteelpark Arenberg, Leuven B-3001, Belgium
3. Katholieke Universiteit Leuven, Institute for Nanoscale Physics and Chemistry (INPAC), Celestijnenlaan 200 D, Leuven B-3001, Belgium

Abstract

Mn doped II-IV-V2 chalcopyrites are promising candidates for room temperature ferromagnetic semiconductors. Although several materials such as CdGeP2:Mn, ZnGeP2:Mn have already been reported as room temperature ferromagnetic semiconductors, most of them are bulk materials synthesized at high temperature.

Among this category, we chose MgGeAs2:Mn as a new candidate for MBE growth on GaAs substrates. Before the study of Mn doping, 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 surface roughening. On GaAs (111)B, we obtained single crystalline films of 35nm with a smooth surface and a lattice constant of 5.66Å at an optimized growth temperature of 600oC and a BEP flux ratio Mg:Ge:As = 1:3.1:800. With flux variations of ±10%, Hall measurements at room temperature showed n-type conduction (n = 2e18~3e18) in Ge rich samples and p-type conduction (p = 4e17~2e19) in Mg rich samples.

Two ways of Mn incorporation were tried on (111)B grown MgGeAs2: (1) in-situ solid state reaction by annealing a Mn layer deposited on top of MgGeAs2 film at 600oC and (2) co-evaporation of Mn during the host material growth. Using both methods, Mn was incorporated by replacing 20% of Mg without structural change. RHEED and XRD did not reveal the existence of additional phases. A more detailed investigation by TEM is in progress. Magnetic properties are studied by VSM, SQUID, and magnetotransport measurements.

 

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Presentation: Oral at E-MRS Fall Meeting 2006, Symposium E, by Zhen Li
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-12 12:00
Revised:   2009-06-07 00:44