  The Belle II experiment at the Super B factory SuperKEKB, an asymmetric
$e^+e^-$ collider located in Tsukuba, Japan, is tailored to perform precision B
physics measurements. The centre of mass energy of the collisions is equal to
the rest mass of the $\Upsilon(4S)$ resonance of $m_{\Upsilon(4S)} = 10.58\,\rm
GeV$. A high vertex resolution is essential for measuring the decay vertices of
B mesons. Typical momenta of the decay products are ranging from a few tens of
MeV to a few GeV and multiple scattering has a significant impact on the vertex
resolution. The VerteX Detector (VXD) for Belle II is therefore designed to
have as little material as possible inside the acceptance region. Especially
the innermost two layers, populated by the PiXel Detector (PXD), have to be
ultra-thin. The PXD is based on DEpleted P-channel Field Effect Transistors
(DEPFETs) with a thickness of only $75\,\rm\mu m$. Spatial resolution and hit
efficiency of production detector modules were studied in beam tests performed
at the DESY test beam facility. The spatial resolution was investigated as a
function of the incidence angle and improvements due to charge sharing are
demonstrated. The measured module performance is compatible with the
requirements for Belle II.
