Effects of hydrogen implantation into GaN

Abstract

Proton implantation in GaN is found to reduce the free carrier density through two mechanisms – first, by creating electron and hole traps at around E C − 0.8 eV and E V + 0.9 eV that lead to compensation in both n- and p-type material, and second, by leading to formation of (AH)° complexes, where A is any acceptor (Mg, Ca, Zn, Be, Cd). The former mechanism is useful in creating high resistivity regions for device isolation, whereas the latter produces unintentional acceptor passivation that is detrimental to device performance. The strong affinity of hydrogen for acceptors leads to markedly different redistribution behavior for implanted H + in n- and p-GaN due to the chemical reaction to form neutral complexes in the latter. The acceptors may be reactivated by simple annealing at ⩾600°C, or by electron injection at 25–150°C that produces debonding of the (AH)° centers. Implanted hydrogen is also strongly attracted to regions of strain in heterostructure samples during annealing, leading to pile-up at epi–epi and epi–substrate interfaces. IR spectroscopy shows that implanted hydrogen also decorates V Ga defects in undoped and n-GaN.