Zn-Doped P-Type Gallium Nitride Through Nuclear Transmutation Doping Processes

For the last decades, Zinc (Zn) has been studied as a p-type dopant for gallium nitride (GaN) as an alternative to magnesium although high-quality doping was unachievable. Here, we introduce ways to produce p-type GaN with uniformly doped Zn using nuclear transmutation doping processes.<br/><br/>First, we found that photonuclear transmutation doping (PNTD) is one of the promising ways for high-quality Zn doping. In collaboration with Argonne National Laboratory (ANL), GaN with a large number of Zn was obtained by controlling the beam energy for the PNTD process and we found p-type properties from the Zn-doped GaN. The uniform Zn distribution in the crystal was confirmed by using secondary-ion mass spectrometry (SIMS) measurements. In addition, the transmutation doping concentration of Zn was modeled by gamma-ray spectroscopy, Monte Carlo-based simulation program, and a nuclear data library. The concentration of Zn produced by the PNTD turns out to be 2.25×10¹⁷/cm³. Hall-effect measurement indicated that the hole carrier concentration was 8.802×10¹⁶/cm³ and I-V characteristics of diodes fabricated from Zn-doped GaN support the p-type characteristics.<br/><br/>Second, proton transmutation doping (PTD) is also considered to be another nuclear transmutation doping process for Zn-doped p-type GaN. Zn production through the PTD process was simulated and we found that Zn production is maximally dominating when the proton energy is around 46 MeV. Unlike PNTD, however, the PTD process will leave the radioactivity concerns due to ⁶⁸Ge (T_1/2 = 270.95 days).