  For already a decade the field of diluted magnetic semiconductors (DMS) is
one of the hottest. In spite of the great success of material specific Density
Functional Theory (DFT) to provide accurately critical Curie temperatures
($T_{C}$) in various III-V based materials, the ultimate search for a unifying
model/theory was still an open issue. Many crucial questions were still without
answer, as for example: Why, after one decade, does GaMnAs still exhibit the
highest $T_{C}$? Is there any intrinsic limitations or any hope to reach room
temperature? How to explain in a unique theory the proximity of GaMnAs to the
metal-insulator transition, and the change from RKKY couplings in II-VI
materials to the double exchange regime in GaMnN? The aim of the present work
is to provide this missing theory. We will show that the key parameter is the
position of the Mn level acceptor and that GaMnAs has the highest $T_{C}$ among
III-V DMS. Our theory (i) provides an overall understanding, (ii) is
quantitatively consistent with existing DFT based studies, (iii) able to
explain both transport and magnetic properties in a broad variety of DMS and
(iv) reproduces the $T_{C}$ obtained from first principle studies for many
materials including both GaMnN and GaMnAs. The model also reproduces accurately
recent experimental data of the optical conductivity of GaMnAs and predicts
those of other materials.
