Donor-hydrogen complexes in crystalline silicon

Summary Experimental results are presented on the study of Sb-H complexes in crystalline silicon, employing¹¹⁹Sb→¹¹⁹Sn source M?ssbauer spectroscopy and a low-energy H implantation technique. In addition to a visible component, we observe a large decrease of the M?ssbauer intensity associated with the trapping of hydrogen, even at low temperatures. This is interpreted as the formation of a component with a negligible recoilless fraction. The different M?ssbauer components were studied as a function of H dose, H-implantation temperature and annealing temperature. The data show that the visible component is associated with the well-known SbH complex, whereas the invisible component is associated with the formation of SbH _n (n≥2) complexes. We show that these complexes are in thermal equilibrium with a larger hydrogen reservoir (H ₂ ^* ), which governs their thermal stability. No Sb-H complexes are observed inp-type Si after H-implantation, in agreement with the current belief that hydrogen has a deep donor level in the gap. The microscopic structure of the various Sb-H and Sn-H complexes was studied with first-principles calculations using the pseudopotentialdensity-functional approach. The structure of the Sb-H complex is found to be similar to the P-H complex, with the H in an antibonding site of a Si atom neighbouring the Sb impurity. For SbH₂ three configurations are found with energies differing by less than ≈ 0.1 eV. We find that the reaction SbH+H≠SbH₂ is exothermic. We argue that the SbH₂ complexes are shallow donors, irrespective of the structure. Therefore, the formation of SbH₂ may depassivate the sample. Paper presented at ICAME-95, Rimini, 10–16 September 1995.     

Radiative processes in bulk crystalline silicon

For the luminescence from optical centres in bulk silicon to be of use in opto-electronic devices the silicon should emit at room temperature at a well-defined wavelength, with a minimum of heat generation, and with a high quantum efficiency. These criteria are not satisfied. The reasons are reviewed in terms of the intrinsic properties of typical centres and of effects which are extrinsic to the centres.     

States of hydrogen in crystalline silicon

The thermal transformation of deuterium in p-type crystalline silicon is studied with a variety of experimental techniques. It is found that D-atoms initially trapped at acceptor sites can be transferred by low temperature annealing to a different state tentatively ascribed to interstitial D₂ molecules. Diffusion of D out of the passivated sample only occurs at temperatures significantly higher than this transformation temperature. This fact allows us to produce Si samples with extremely high deuterium concentrations (several at%) by a suitable passivation-annealing sequence. With increasing D-concentration, a number of characteristic Si-D defect complexes have been observed by vibrational spectroscopy.     

Hydrogen in phosphorus- and carbon-doped crystalline silicon

The formation kinetics of the H-C complex in P-doped silicon have been studied using the DLTS and C-V profiling methods. The measurements show that the hydrogen species that is incorporated in the H-C complex originates from H-P complexes which act as a “hydrogen reservoir”. The dissociation energy of the H-P complexes is determined to be 1.13 eV. The results of C-V measurements clearly indicate that there exists a negatively charged H-species after the dissociation of the H-P complexes. H motion in an electric field seems to occur via a “hopping mechanism”.     

光管理在晶体硅电池中的应用

光管理是提高晶体硅太阳能电池光吸收和短路电流（Jsc）进而提高转换效率的重要因素之一。本文回顾了最常见的光管理方式,包括表面抗反射、散射以及陷光等。为了降低晶体硅电池的表面反射损失,开发了多种表面抗反射结构。例如,仿生蛾眼结构利用渐变折射率实现了宽光谱低反射率,其表面反射率可达1％以下。随着晶体硅电池衬底减薄,光管理要求更加严格,除了在更宽波长范围内达到超低反射率外,还需要在更高的入射角范围内实现低反射率。此外,利用前表面散射以及背表面陷光结构提高红外光的吸收光程对于晶体硅电池特别是薄衬底晶体硅电池的有效光吸收具有重要意义。     

Hydrogen in the near-surface of crystalline silicon

Abstract

Real-time electric field drift experiments, in-situ capacitance-voltage profiling, deep-level transient spectroscopy and nuclear reaction analysis have been used to monitor hydrogen motion and passivation processes in silicon. Spontaneous hydrogen injection and very fast migration has been detected in the near-surface region of various Schottky barriers and p-n junctions. The effective hydrogen diffusivity is about 10^?8 cm²/s at 400 K in agreement with the estimated value obtained by extrapolation from the high-temperature diffusivity data. The results of real-time in-situ measurements clearly demonstrate that the fast diffusing protons are involved in the hydrogenation processes of both shallow and deep levels. The possible physicochemical mechanisms for the observed spontaneous hydrogen injection which results in unintentional hydrogenation of the subsurface of silicon, and probably other semiconductors, are discussed.     

钙钛矿/晶硅叠层太阳能电池的研究进展

有机—无机杂化钙钛矿电池因其禁带宽度可调、光吸收系数高、光电转化效率高、制备成本低等优点而被用于硅基叠层太阳能电池中,使得太阳能电池的转换效率提高,生产成本降低,应用范围也更为广泛。文章介绍了钙钛矿吸收材料和钙钛矿/晶硅叠层电池的工作原理,对钙钛矿/晶硅叠层电池的类别、影响其性能的主要因素进行了归纳综述,对钙钛矿/晶硅叠层电池未来发展进行了展望。     

Theoretical analysis of impurity distributions in crystalline silicon

Calculations of the total energy of oxygen and carbon impurities in silicon at T=0 K are presented. The equilibrium position of point defects is determined for low (10⁻³–10⁻² at. %) concentrations. Fiz. Tverd. Tela (St. Petersburg) 39, 2001–2002 (November 1997)     

Vibrational lifetime of bond-center hydrogen in crystalline silicon

The lifetime of the stretch mode of bond-center hydrogen in crystalline silicon is measured to be T1 = 7.8+/-0.2 ps with time-resolved, transient bleaching spectroscopy. The low-temperature spectral width of the absorption line due to the stretch mode converges towards its natural width for decreasing hydrogen concentration C(H), and nearly coincides with the natural width for C(H) approximately 1 ppm. The lifetimes of the Si-H stretch modes of selected hydrogen-related defects are estimated from their spectral widths and shown to range from 1.6 to more than 37 ps.     

Ion-beam synthesis of InAs nanocrystals in crystalline silicon

The formation of nanodimensional InAs crystallites on Si wafers was studied by the method of high-fluence implantation of As and In ions with subsequent high-temperature treatment. It was found that the size and depth distributions of the crystallites depend on both the implantation temperature and the annealing conditions. A broad band in an energy range of 0.75–1.1 eV was recorded in the photoluminescence spectra of the samples.