  We report a novel approach for crafting robust diamond/\b{eta}-Ga2O3
hetero-p-n-junctions through the mechanical integration of their bulk
materials. This resulting heterojunction, with a turn-on voltage of ~2.7 V at
room temperature, exhibits resilient electrical performance across a
temperature spectrum up to 125{\deg}C, displaying minimal hysteresis-measuring
as low as 0.2 V at room temperature and below 0.7 V at 125{\deg}C. Remarkably,
the ideality factor achieves a record low value of 1.28, setting a new
benchmark for diamond/ \b{eta}-Ga2O3 heterojunctions. The rectification ratio
reaches over 10^8 at different temperatures. This effortlessly fabricated and
remarkably resilient diamond/Ga2O3 hetero-p-n-junction pioneers a novel pathway
for the exploration and fabrication of heterojunctions for ultra-wide bandgap
semiconductors with substantial lattice mismatch and different thermal
expansion coefficients.
