Thermodynamic limits to the maximum Curie temperature in Ga1-xMnxAs

Conference · Fri Jul 19 04:00:00 EDT 2002

OSTI ID:803855

Yu, K M ^[1]; Walukiewicz, W; Wojtowicz, T; Kuryliszyn, I; Liu, X; Sasaki, Y; Furdyna, J K

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1. LBNL Library

Using the ion channeling techniques we find that a substantial fraction (up to 15%) of the Mn atoms reside in interstitial sites in Ga{sub 1-x}Mn{sub x}As alloys (with x ranging from 0.02 to 0.09). Moreover, the T{sub C} of Ga{sub 1-x}Mn{sub x}As is found to be very sensitive to annealing at temperatures close to the growth temperature of 265 C. Ion channeling results demonstrate that the increase of TC after annealing at 282 C can be attributed to a relocation of Mn atoms from interstitial sites to form random clusters. A series of Ga{sub 1-x-y}Mn{sub x}Be{sub y}As layers, in which the magnetic moments and free holes are independently controlled by the Mn and Be contents, respectively, are also investigated. A dramatic increase of the concentration of Mn interstitials and a reduction of T{sub C} are observed as the Be concentration increases, while the free hole concentration stays relatively constant at {approx}5x10{sup 20}cm{sup -3}. These results demonstrate that the concentrations of free holes as well as uncompensated Mn spins are governed by the position of the Fermi level, which controls the formation energy of compensating interstitial Mn acceptors. This Fermi-level-induced hole saturation is responsible for the commonly observed upper limit of 110 K for the Curie temperature of this material system.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: USDOE Director, Office of Science. Office of Basic Energy Studies. Materials Science and Engineering Division (US)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 803855
• Report Number(s): LBNL--51165; B& R KC0201030
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALLOYS
ANNEALING
ATOMS
CURIE POINT
FERMI LEVEL
INTERSTITIALS
ION CHANNELING
MAGNETIC MOMENTS
PHYSICS
SATURATION
THERMODYNAMICS