Theoretical models of Schottky-barrier height formation are reviewed. A particular emphasis is placed on the examination of how these models agree with general physical principles. New concepts on the relationship between interface dipole and chemical bond formation are analyzed, and shown to offer a coherent explanation of a wide range of experimental data.

Recent advances in Schottky barrier concepts

The formation of the Schottky barrier height (SBH) is a complex problem because of the dependence of the SBH on the atomic structure of the metal-semiconductor (MS) interface. Existing models of the SBH are too simple to realistically treat the chemistry exhibited at MS interfaces. This article points out, through examination of available experimental and theoretical results, that a comprehensive, quantum-mechanics-based picture of SBH formation can already be constructed, although no simple equations can emerge, which are applicable for all MS interfaces. Important concepts and principles in physics and chemistry that govern the formation of the SBH are described in detail, from which the experimental and theoretical results for individual MS interfaces can be understood. Strategies used and results obtained from recent investigations to systematically modify the SBH are also examined from the perspective of the physical and chemical principles of the MS interface.

The physics and chemistry of the Schottky barrier height

+ -Si/p + -GaAs junctions showed excellent linearity. The interface resistance of n + -Si/n + -GaAs junctions was found to be 0.112 Ω&cm 2 , which is the smallest value observed in all the samples. The resistance decreased with increasing annealing temperature and decreased to 0.074 Ω&cm 2 after the junction annealing at 400°C. These results demonstrate that n + -Si/n + -GaAs junctions are suitable for the connection of subcells in the fabrication of tandem solar cells. © 2015 The Japan Society of Applied Physics

https://iopscience.iop.org/article/10.7567/JJAP.54.030211/pdf

Investigation on the interface resistance of Si/GaAs heterojunctions fabricated by surface-activated bonding

Effects of annealing on surface-activated bonding (SAB)-based Si/Si junctions were investigated by transmission electron microscopy (TEM) observations and current–voltage (I–V) measurements. We observed an amorphous-like layer at the bonding interface, which was recrystallized by annealing. We extracted the potential barrier heights at Si/Si interfaces annealed at different temperatures from the results of I–V measurements at various ambient temperatures. For p-Si/p-Si junctions, the barrier height increased as the annealing temperature increased from 200 to 400 °C and decreased from 400 to 1000 °C. For n-Si/n-Si junctions, the barrier height increased as the annealing temperature increased from 200 to 600 °C and decreased from 600 to 1000 °C. By using the charge neutral level (CNL) model, we estimated the energy of CNL, ECNL, and the density of interface states, Dit, at each annealing temperature. Dit decreased as the annealing temperature increased from 400 to 1000 °C. ECNL showed values larger than the reported ones.

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Effects of annealing on electrical properties of Si/Si junctions by surface-activated bonding

Current–voltage (I–V) and capacitance–voltage (C–V) characteristics of He-ion irradiated Pd/n-Si09Ge0.10 Schottky contacts have been measured in the temperature range from 100 to 300 K. Schottky barrier properties such as the Schottky barrier height (Φbn) and ideality factor (n) have been studied as a function of temperature. The degree to which their characteristics deviated from the ideal case increased as the temperature decreased. A decrease in Φbn and an increase in n with decreasing temperature are observed. Additionally, linear dependence between the so-called temperature factor T0 and temperature as well as between Φbn and n are shown. This type of strong temperature dependence indicates the presence of a large degree of lateral inhomogeneities of the barrier height, resulting from the He-ion irradiation induced defects and traps which produce a variation in the number of free carriers. The presence of electrically active defects introduced by He-ion irradiation at and below the Si0.90Ge0.10 surface support this interpretation.

https://iopscience.iop.org/article/10.1088/0022-3727/40/5/007/pdf

Influence of He-ion irradiation on the characteristics of Pd/n-Si0.90Ge0.10/Si Schottky contacts

The electrical characteristics of Schottky diodes fabricated on silicon surfaces subject to low‐energy (10 keV) argon ion implantation have been studied as a function of Ar+ ion dose. Significant changes in electrical characteristics are seen for ion doses as low as 5×1011 cm−2, well below the amorphization threshold dose for Si. In conjunction with the ion energy threshold established earlier for Si surface damage effects (∼25 eV), these results outline fundamental limits on the effect of ion‐assisted dry etching processes on Si surface barriers.

H. Beneking

Papers

Effect of argon ion implantation dose on silicon Schottky barrier characteristics

Effect of low energy Ar+ ion implantation on silicon surface barriers