Grain-boundary space-charge conduction

Abstract

Recent research on silicon grain boundaries has confirmed the typical features known from earlier work on grain boundaries in germanium and III-V compound semiconductors. However, there is less clarity with respect to the role of the ‘‘dangling bonds’’ when testing for electrical activity. In silicon a pronounced double barrier with its space-charge layer and a low leakage current rarely forms. Here the Cottrell atmospheres in conjunction with impurity complexes such as SiO, SiO2, and SiO4 can strongly influence the electrical properties in a material with an exceptionally high self-diffusivity. Conditions for the measurability of the longitudinal impurity band-type conduction through space-charge layers in silicon grain boundaries are outlined. It is concluded that in those cases where electrical activity is measured, the conduction parallel to the grain-boundary plane should be apparent for pure material and at low temperature. Experiments are proposed to further our understanding of the properties of grain boundaries in silicon.

Defect alignment in grain boundaries as quantum wells

“…3,4 Within such a structure the carrier mobility is higher than in the degeneratively doped bulk crystal. [3][4][5] Figure 1 shows the model for a pure tilt boundary with alternating dilation-and compressioncaused band-gap variations, as it has been proposed to explain some of the outstanding features ͑from Ref. 4, see also Ref.…”

On the origin of the electrical activity in silicon grain boundaries

“…Polycrystalline semiconductors are used in device technology in two opposite directions : either as passive components with specific properties due to the presence of the grain boundaries, either as active components, despite these same properties [1][2][3][4][5][6][7][8]. In the first category, one may find baryum titanate capacitors, zinc oxyde varistors and polycrystalline silicon interconnections ; in the second are situated bulk poly-Si solar cells and thin-film poly-Si field effect transistors.…”

“…The book of this School [4] is certainly the most detailed in the smallest form to tackle this theme. Recent reviews by Mataré [5][6], Grovenor [7] and Seager [8] are also available on the subject. Grovenor is the most complete and presents very clearly the metallurgical side of the problem.…”

“…As the charge carrier transport at GB is well developed in these works it is not going to be presented here. The reader interested in the subject will particularly report to Seager (transport perpendicular to the GB plane) [8] and to Mataré (transport along the GB plane) [5][6].…”

“…There are two ways for the GB disordered zones to create gap states : either with the intrinsic crystallographic mismatch, either because of the extrinsic presence of segregated defects or impurities. Among the large amount of experimental studies performed on the subject [1][2][3][4][5][6][7][8], only a few permit the direct Fig. 1.…”