Hydrogen passivation of Ca acceptors in GaN

Abstract

Exposure to a hydrogen plasma at 250 °C of p-type GaN (Ca) prepared by either Ca+ or Ca+ plus P+ co-implantation leads to a reduction in sheet carrier density of approximately an order of magnitude (1.6×1012 cm−2 to 1.8×1011 cm−2), and an accompanying increase in hole mobility (6 cm2/V s to 18 cm2/V s). The passivation process can be reversed by posthydrogenation annealing at 400–500 °C under a N2 ambient. This reactivation of the acceptors is characteristic of the formation of neutral (Ca–H) complexes in the GaN. The thermal stability of the passivation is similar to that of Mg–H complexes in material prepared in the same manner (implantation) with similar initial doping levels. Hydrogen passivation of acceptor dopants in GaN appears to be a ubiquitous phenomenon, as it is in other p-type semiconductors.

Incorporation of Deep Defects in GaN Induced by Doping and Implantation Processes

“…With increasing doping cell temperature the NBG peak shifts from 30 meV (undoped samples) to 250 and 170 meV below gap for magnesium and calcium doping, respectively. These values are in good agreement with the energy levels for magnesium (170 to 290 meV [8,9]) and calcium (169 meV [2,10]) reported in the literature. However, the OAS spectrum of the highest calcium doped sample exhibits only a broad superposition of the NBG peak and the neighbouring BB.…”

“…Currently, magnesium is the acceptor of choice. However, because of the relatively high activation energy of the magnesium acceptor, alternative acceptor doping elements are searched, such as calcium [2] or carbon [3].…”

Hydrogen Induced Yellow Luminescence in GaN Grown by Halide Vapor Phase Epitaxy

“…18 It can be both intentionally or unintentionally introduced into the epilayer during growth [19][20][21] or post-growth processing, such as plasma-hydrogenation, 18,[22][23][24][25] high-temperature annealing in NH 3 , 26 and even wet or dry-etching. 18 It can be both intentionally or unintentionally introduced into the epilayer during growth [19][20][21] or post-growth processing, such as plasma-hydrogenation, 18,[22][23][24][25] high-temperature annealing in NH 3 , 26 and even wet or dry-etching.…”

Efficient Acceptor Activation in AlxGa1−xN/GaN Doped Superlattices

“…The large activation energy of Mg of 150 meV to 250 meV 1,2,3 results in a low acceptor ionization probability. Other acceptors such as Be and Ca also have large activation energies of 150 meV 4 and 169 meV 5 , respectively. The low acceptor activation in p-type GaN results in large series resistances and high operating voltages, thereby adversely affecting the performance of electronic and optoelectronic devices.…”