Positron studies of compensating defects in n-type ultra wide band gap III-nitrides and III-oxides

Si is the n-type dopant of choice for GaN and β-Ga₂O₃. However, in ultra wide band gap (Al,Ga)N and β-(Al,Ga)₂O₃ alloys, the n-type conductivity produced by the added Si impurities is efficiently compensated above a threshold Al content. The critical Al fractions are about 80% for the (Al,Ga)N alloys and as low as 30% for the β-(Al,Ga)₂O₃ alloys [1, 2]. AlN and Al₂O₃ are well known to be poorly n-type dopable even with Si, but the detailed compensation mechanisms in the alloys are not necessarily the same as in the alloys.

Positron annihilation spectroscopy is a useful method for studying neutral and negatively charged vacancy-type defects, as well as negatively charged defects with no open volume such as acceptor impurities [1]. I will discuss the most recent results obtained in Si-doped (Al,Ga)N and β-(Al,Ga)₂O₃ alloys in the light of the compensation phenomena caused by cation vacancies, carbon impurities and Si autocompensation. The local environment of the Si dopants appears to have a strong impact on the doping efficiency.

[1] X. T. Trinh et al., Appl. Phys. Lett. 105, 162106 (2014).

[2] Z. Galazka et al., J. Appl. Phys. 113, 035702 (2023).

[3] F. Tuomisto and I. Makkonen, Rev. Mod. Phys. 85, 1583 (2013).