Highly enhanced Curie temperature in low-temperature annealed [Ga,Mn]As epilayers

We report Curie temperatures up to 150 K in annealed Ga1−xMnxAs epilayers grown with a relatively low As:Ga beam equivalent pressure ratio. A variety of measurements (magnetization, Hall effect, magnetic circular dichroism and Raman scattering) suggest that the higher Curie temperature results from an enhanced free hole density. The data also indicate that, in addition to the carrier concentration, the sample thickness limits the maximum attainable Curie temperature in this material, suggesting that the free surface of Ga1−xMnxAs epilayers may be important in determining their physical properties.

[1]  Yoshiaki Hashimoto,et al.  Effect of low-temperature annealing on transport and magnetism of diluted magnetic semiconductor (Ga, Mn)As , 2001 .

[2]  Effects of annealing time on defect-controlled ferromagnetism in Ga1−xMnxAs , 2001, cond-mat/0105541.

[3]  Saturated ferromagnetism and magnetization deficit in optimally annealed Ga 1 − x Mn x As epilayers , 2002, cond-mat/0204250.

[4]  Masaaki Tanaka,et al.  Magneto-optic effect of the ferromagnetic diluted magnetic semiconductor Ga1−xMnxAs , 1998 .

[5]  H. Ohno,et al.  Zener model description of ferromagnetism in zinc-blende magnetic semiconductors , 2000, Science.

[6]  E. Johnston-Halperin,et al.  (Ga,Mn)As as a digital ferromagnetic heterostructure , 2000 .

[7]  D. Awschalom,et al.  Semiconductor spintronics and quantum computation , 2002 .

[8]  Hideo Ohno,et al.  Magnetic Circular Dichroism Studies of Carrier-Induced Ferromagnetism in ( Ga 1 − x Mn x ) As , 1999 .

[9]  H. Ohno,et al.  (Ga,Mn)As: A new diluted magnetic semiconductor based on GaAs , 1996 .

[10]  Curie Temperature Trends in (III,Mn)V Ferromagnetic Semiconductors , 2002, cond-mat/0201157.

[11]  C. Foxon,et al.  High-Curie-temperature Ga1−xMnxAs obtained by resistance-monitored annealing , 2002, cond-mat/0209554.

[12]  Tomasz Wojtowicz,et al.  Effect of the location of Mn sites in ferromagnetic GaMnAs on its Curie temperature , 2002 .

[13]  H. Ohno,et al.  Transport properties and origin of ferromagnetism in (Ga,Mn)As , 1998 .