Crystallization of amorphous hydrogenated Si1−xGex films

Abstract

The incubation time t0 of the crystallization of intrinsic and P, B‐doped amorphous silicon‐germanium (a‐Si1–xGex: H) layers deposited on SiO2/Si(100) substrates is studied as a function of temperature and composition using in situ transmission electron microscopy (TEM). The temperature dependence of t0 follows an Arrhenius behavior t0 = t0* exp (W/kT) with activation energy W and prefactor t0* depending on x. The dependences of grain growth, nucleation rate as well as of the morphology of the polycrystalline films on temperature, doping, and composition are estimated. Doping SiGe films with B decreases grain growth rate during crystallization. Independent of the Ge content, such films stay nanocrystalline (grain size ≪10 nm) up to an annealing temperature of 800°C. During crystallization decomposition within SiGe films is observed. Furthermore, metal‐induced crystallization in the Al/a‐Si1–xGex:H structures is demonstrated.

Mechanisms of photosensitivity in germanosilica films

“…22,23 In the case of PECVD of Ge-doped silica, the required level of ion bombardment necessary to cause amorphization of the growing film, is likely to be higher than that for pure silica as germanium increases the probability of nucleation and cluster formation. 24 Indeed, the non-ion-bombarded, Ge-doped silica films exhibit columnar structure ͓Fig. 5͑b͔͒, whereas no such structure was observed in the pure silica films deposited in this study under similar conditions.…”

Crystallization of amorphous Si0.5Ge0.5films studied by means ofin-situX-ray diffraction andin-situtransmission electron microscopy

“…The change in n reflects a typical crystallization process in thin films, which starts as a 3D process when the crystals are small and transforms to a 2D process when the grain size D , reaches the film thickness d . When N is high and vg low, as was observed earlier in Sil-,Ge,v : H : B films (Edelman et al 1995) and Sil-,Ge, : Ga (Edelman et al 1996(Edelman et al , 1997, the crystallization resulted in a nanocrystalline structure, typical of a 3D mode, at temperatures between 500 and 850°C. However, in this case, the Sio.5Geo.5 films (both undoped and B doped) crystallized in a mode in which N is relatively low but wg is relatively high.…”

“…Some studies of SPC in hydrogenated a-Si,-,Ge, (a-Si,-,Ge,:H) (x = 0 to l), undoped and highly doped with B or P, were recently carried out and demonstrated the strong iduence of doping on the crystallization parameters (Edelman et al 1995).…”

“…Therefore, the temperature dependence of T is T = .ro exp-( W / k T ) , where W is the overall activation energy of crystallization and is given by W = ( H + 3E)/4 (3D case) or W = ( H + 2E)/3 (2D case). The incubation time to of crystallization was evaluated by in-situTEM (Edelman et al 1995) by defining it as the time necessary for a crystallite to grow large enough to be detectable by TEM (about 10nm). At that time to, the crystalline fraction f ( t o ) M 0.1-1%.…”

Functional networks models for rapid characterization of thin films: An application to ultrathin polycrystalline silicon germanium films

“…5b). Diborane flow rate, on the other hand, does not significantly improve the absorption of Si and Ge atoms and hence a weak dependence of deposition rate and thickness [23] (Fig. 5c).…”