Wet Nitride Research Articles

Carrier Recombination Processes in GaAs Wafers Passivated by Wet Nitridation.

As one of the successful approaches to GaAs surface passivation, wet-chemical nitridation is applied here to relate the effect of surface passivation to carrier recombination processes in bulk GaAs. By combining time-resolved photoluminescence and optical pump—THz probe measurements, we found that surface hole trapping dominates the decay of photoluminescence, while photoconductivity dynamics is limited by surface electron trapping. Compared to untreated sample dynamics, the optimized nitridation reduces hole- and electron-trapping rate by at least 2.6 and 3 times, respectively. Our results indicate that under ambient conditions, recovery of the fast hole trapping due to the oxide regrowth at the deoxidized GaAs surface takes tens of hours, while it is effectively inhibited by surface nitridation. Our study demonstrates that surface nitridation stabilizes the GaAs surface via reduction of both electron- and hole-trapping rates, which results in chemical and electronical passivation of the bulk GaAs surface.

Real Time Infra-Red Absorption Analysis of Nitridation of GaAs(001) by Hydrazine Solutions

The chemical bonds established on GaAs(001) by wet nitridation in hydrazine solutions containing 0.01 M of sodium sulfide are investigated using in-situ IR absorption spectroscopy. Hydrazine distillation is found to be necessary in order to avoid numerous carbon-related features in the spectra. The absorption spectrum consists of positive lines due to adsorbed hydrazine molecules and of negative lines due to water being removed from the surface. Well-defined structures near 960 cm−1 and 1020 cm−1 as well as a broader line near 1008 cm−1, not present in the absorption spectrum of the solution, also appear. Investigation of isotopic effects, of the effect of plasma nitridation and of the kinetics of the various lines suggests that hydrazine bonding first occurs to surface Ga atoms in a singly-bonded (Ga-NH-NH2) and doubly-bonded GaGa > N − NH2 end-on configuration. At a later stage, dissociative interaction between chemisorbed hydrazine molecules forms the GaGa > NH configuration.