  The lack of p-type doping has impeded the development of vertical gallium
oxide (Ga2O3) devices. Current blocking layers (CBL) using implanted deep
acceptors has been used to demonstrate vertical devices. This paper presents
the first demonstration of in situ Mg-doped beta-Ga2O3 CBLs grown using
metalorganic chemical vapor deposition. Device structures were designed with
in-situ Mg doped layers with varied targeted Mg doping concentrations, which
were calibrated by quantitative secondary ion mass spectroscopy (SIMS). The
effectiveness of the CBL is characterized using temperature dependent
current-voltage measurements using n-Mg-doped-n structures, providing crucial
insight into the underlying mechanisms. To further validate the experimental
results, a TCAD simulation is performed and the electrically active effective
doping is found to be dependent on the Mg-doping density, offering a new
perspective on the optimization of CBL performance. Breakdown measurements show
a 3.4 MV/cm field strength. This study represents a significant step forward in
the development of Ga2O3-based devices and paves the way for future
advancements in this exciting field.
