**7. Summary**

GaN SBDs have demonstrated grea<sup>t</sup> potential in radiation detection on the virtue of its high displacement energy, wide bandgap and critical electric field strength. Conventionally, GaN particle detectors employ either a thin GaN epitaxial layer on the hetero-epitaxial substrate or thick free-standing GaN substrate to fabricate a radiation detector. While the thin epi-layer detector worked at low voltages (−28 V) with high CCE, they are only able to detect very low energies (< 1 MeV). The defects present in GaN such as high TDD and unintentional doping, have been the major constraints in terms of improving the detector performance. With improvement in growth technologies, free-standing GaN

detectors with low TDD and doping densities have been fabricated which has increased the detected energy (5.48 MeV) but they require very high voltages (−550 V) to detect these energies with 100% CCE.

High performing GaN α-particle detector can be achieved by designing a thin compensated GaN DL on conducting GaN substrate. Compensation of thin DL by doping p-type (Mg) ions in DL reduces the CCD generated by unintentional n-type doping. The increase in DW can reduce the JR and increased the VBD without affecting the ideality factor and barrier height of the SBDs. A ~3 times improvement in VBD from 430 V to 1480 V due to compensation has helped realize SBDs with the highest reported VBD at 2400 V (SBDs with 30 μm DL) without any additional termination or field plates.

The improvement in reverse characteristics have helped in improvement of the performance of the detector by improving the sensitivity and reducing the voltage requirement of the detector. These compensated GaN-on-GaN SBDs exhibit a 30% increase in CCE (65%) at low voltages (−20 V) in comparison to previously reported GaN α-particle detectors. High CCE of 96.7% was also measured at −300 V, which is 250 V lower than the previously reported bias requirement. The improved performance in α-particle detection is due to the formation of thicker DW at low voltages. The spectral resolution of 71 keV is also 30% better than the previous reports. Presence of air results in scattering of α-particle incident on the detector, which in turn reduced its e fficiency by ~7%. While detectors with thicker DW do require a higher voltage (750 V) to detect α-particles with 100% CCE, they can also detect higher energies (9.1 MeV).

**Author Contributions:** A.S. along with S.A. and N.G.I. have designed the experiments; Simulations and fabrication of devices was completed by A.S.; Result analysis was completed by A.S., S.A. and N.G.I.; J.K. performed radiation detection testing and analysis.; S.N. and H.A. have grown the GaN material for fabrication of devices; A.S. wrote the paper, which was reviewed by all authors. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding

**Conflicts of Interest:** The authors declare no conflict of interest.
