  Electrically driven light sources are essential in a wide range of
applications, from indication and display technologies to high-speed data
communication and quantum information processing. Wide-bandgap semiconductors
promise to advance solid-state lighting by delivering novel light sources.
However, electrical pumping of these devices is still a challenging problem.
Many wide-bandgap semiconductor materials, such as SiC, GaN, AlN, ZnS, and
Ga2O3, can be easily doped n-type, but their efficient p-type doping is
extremely difficult. The lack of holes due to the high activation energy of
acceptors greatly limits the performance and practical applicability of
wide-bandgap semiconductor devices. Here, we study a novel effect which allows
homojunction semiconductors devices, such as p-i-n diodes, to operate well
above the limit imposed by doping of the p-type material. Using a rigorous
numerical approach, we show that the density of injected holes can exceed the
density of holes in the p-type injection layer by up to three orders of
magnitude, which gives the possibility to significantly overcome the doping
problem. We present a clear physical explanation of this unexpected feature of
wide-bandgap semiconductor p-i-n diodes and closely examine it in 4H-SiC,
3C-SiC, AlN and ZnS structures. The predicted effect can be exploited to
develop bright light emitting devices, especially electrically driven
non-classical light sources based on color centers in SiC, AlN, ZnO and other
wide-bandgap semiconductors.
