  The large tunneling anisotropic magneto-resistance of a single
$p^{++}$-(Ga,Mn)As/$n^{+}$-GaAs Zener-Esaki diode is evidenced in a
perpendicular magnetic field over a large temperature and voltage range. Under
an applied bias, the tunnel junction transparency is modified, allowing to
continuously tune anisotropic transport properties between the tunneling and
the ohmic regimes. Furthermore, an asymmetric bias-dependence of the
anisotropic tunneling magneto-resistance is also observed: a reverse bias
highlights the full (Ga,Mn)As valence band states contribution, whereas a
forward bias only probes part of the density of states and reveals opposite
contributions from two subbands.
