Neutralization of Shallow Dopants in III-V Compounds

Molecular hydrogen atmosphere is the less aggressive method but, as we shall see, decomposition of the H2 molecules at the surface is the limiting process for its introduction. In this section, we shall present mainly results concerned with hydrogen plasma introduction. Comparison will be made with other introduction methods. We shall present also the effect of nonin-tentional introduction of hydrogen in these semiconductors. 

As for silicon, secondary ion mass spectrometry (SIMS) is the most widely used profiling analysis technique for deuterium diffusion studies in III-V compounds. Deuterium advantageously replaces hydrogen for lowering the detection limit. The investigations of donor and acceptor neutralization effects have been usually performed through electrical measurements, low temperature photoluminescence, photothermal ionization spectroscopy (PTIS) and infrared absorption spectroscopy. These spectroscopic investigations will be treated in a separated part of this chapter. 

Exposure of bulk GaAs Si wafers to a capacitively coupled rf deuterium plasma at different temperatures generates deuterium diffusion profiles as shown in Fig. 1. These profiles are close to a complementary error function (erfc) profile. At 240°C, the effective diffusion coefficient is 3 x 10 12 cm2/s. The temperature dependence of the hydrogen diffusion coefficient is given by (Jalil et al., 1990)  

The hydrogen solubility at the sample surface is strongly dependent on the rf power density (Chevallier et al., 1986). 

The deuterium concentration profile is also a function of the silicon doping level of the sample. Pearton et al. (1987b) demonstrated that the 

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