Hydrogenation of Defects in Crystalline Silicon

CENTER FOR OPTOELECTRONIC COMPUTING SYSTEMS DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING UNIVERSITY OF COLORADO AT BOULDER BOULDER, COLORADO 

SOLAR ENERGY RESEARCH INSTITUTE GOLDEN, COLORADO 

The early work of Sakurai and Hagstrum (1976) addressed the question of adsorption of H on the surface of Si crystals. They found that a (111) surface is covered with monohydrides and trihydrides, whereas a (100) surface is covered with monohydrides and dihydrides. The termination of Si dangling bonds by a small H atom allows the lattice perturbed at the surface to restructure or reconstruct itself, as though there were no 

The insights into the role of H gained from the studies of a-Si H are applicable to c-Si. Hence, one should expect that any defect comprising one or more dangling bonds can be passivated by atomic H. As we shall see, the consequences can be dramatic. A more extensive discussion of various defects will be found in Chapter 4 by Corbett et al. 

I shall describe the hydrogenation method I used and then consider the passivation of surface states and that of bulk dangling bonds, including grain boundaries, dislocations and point defects. 

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Noble M. Johnson and Chris G. Van de Walle, Isolated Monatomic Hydrogen in Silicon Yurij V. Gorelldnskii, Electron Paramagnetic Resonance Studies of Hydrogen and Hydrogen-Related Defects in Crystalline Silicon... 

Another effect of hydrogen in crystalline silicon is to break Si—Si bonds. After exposure of the surface to atomic hydrogen, extended defects are found in the surface region, typically to a depth of about 1000 A (Johnson, Ponce, Street and Nemanich 1987). These defects have no Burgers vector and are therefore not dislocations, but rather appear to be microcracks, in which the (111) planes of the crystal are pushed apart. A plausible explanation of the crack is that the silicon atoms are terminated by hydrogen and so are pushed apart. The presence of Si—H bonds is confirmed by Raman scattering. Hydrogen therefore can break Si—Si bonds and has a tendency to disorder the crystal. 

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