Low Voltage High-Energy α-Particle Detectors by GaN-on-GaN Schottky Diodes with Record-High Charge Collection Efficiency

Simulation-Based Analysis of the Effect of Alpha Irradiation on GaN Particle Detectors

Radiation-hardened semiconductor GaN has drawn considerable attention owing to its excellent properties such as large displacement energy. Many studies have focused on evaluating the degradation of GaN-based power device performance by proton beam or particle irradiation, while quantitative analysis of the energy transfer process of particles inside the material and the mechanisms involved in inducing degradation of electrical properties are rare. Here, on the basis of the fabricated alpha-particle detector, a device model validated by basic electrical experiments is established to simulate the influence of alpha-particle irradiation on the leakage current of the device. We observe that the current does not change significantly with increasing radiation fluence at low bias, while it shows a descending trend with increasing radiation fluence at higher bias. However, increasing the energy of the radiation particles at the same radiation fluence directly leads to a monotonically elevated leakage current. Such a series of phenomena is associated with radiation-induced changes in the density of trapped states within the active layers of the device.

Vertical GaN-on-GaN Schottky Diodes as α-Particle Radiation Sensors

Among the different semiconductors, GaN provides advantages over Si, SiC and GaAs in radiation hardness, resulting in researchers exploring the development of GaN-based radiation sensors to be used in particle physics, astronomic and nuclear science applications. Several reports have demonstrated the usefulness of GaN as an α-particle detector. Work in developing GaN-based radiation sensors are still evolving and GaN sensors have successfully detected α-particles, neutrons, ultraviolet rays, x-rays, electrons and γ-rays. This review elaborates on the design of a good radiation detector along with the state-of-the-art α-particle detectors using GaN. Successful improvement in the growth of GaN drift layers (DL) with 2 order of magnitude lower in charge carrier density (CCD) (7.6 × 1014/cm3) on low threading dislocation density (3.1 × 106/cm2) hydride vapor phase epitaxy (HVPE) grown free-standing GaN substrate, which helped ~3 orders of magnitude lower reverse leakage current (IR) with 3-times increase of reverse breakdown voltages. The highest reverse breakdown voltage of -2400 V was also realized from Schottky barrier diodes (SBDs) on a free-standing GaN substrate with 30 μm DL. The formation of thick depletion width (DW) with low CCD resulted in improving high-energy (5.48 MeV) α-particle detection with the charge collection efficiency (CCE) of 62% even at lower bias voltages (-20 V). The detectors also detected 5.48 MeV α-particle with CCE of 100% from SBDs with 30-μm DL at -750 V.