Neutralization of Deep Level Centers and Extended Defects

Neutralization of Deep Level Centers and Extended Defects 

Contrary to the case of shallow impurities, the interaction between deep level defects and hydrogen has been the subject of a few detailed studies. The reasons for that can be found in the lack of detailed understanding of the defect itself involved in the interaction. In some cases, these defects are still the subject of studies with sometimes controversial interpretations. Moreover, the concentration of deep level defects involved in the hydrogen complexes is relatively low, which makes experimental investigations for local structure analysis very difficult. In this section, we present the set of data establishing the neutralization of defects or deep impurities by hydrogen. 

In GaAs, there is a huge number of unidentified deep levels that have been evidenced by DLTS. Some of them depend upon the growth technique. Several works, including early ones, reported the passivation of some of these deep level defects by hydrogenation. 

The partial neutralization by hydrogen of two unidentified electron traps at e - 0.44 eV and Ec - 0.50 eV in bulk GaP has been reported by Pear-ton et al. (1983). It seems that this neutralization is less efficient than for the unidentified electron traps in LEC grown GaAs. 

After plasma hydrogenation for 3 hours at 250°C of horizontal Bridgman grown material, Cho et al. (1988) report a decrease of EL2 ( c — 0.81 eV), EL3 ( c — 0.63 eV) and EL6 ( c - 0.35 eV) electron traps by one order of magnitude. The original concentration of these traps is recovered after thermal annealing at 550°C for 10s. 

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III. Neutralization of Deep Level Centers and Extended Defects... 

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