Thermal Properties and Heat Transport in Silicon‐Based Nanostructures

Abstract

IntroductionFor the past 40 years, crystalline Si (c-Si) continues to be the major material for microelectronics, and modern silicon technology is superior compared to other semiconductors (e.g., II-VI and III-V compounds). In addition to the unique electronic and structural properties of bulk c-Si, silicon dioxide (SiO 2 ) and Si/SiO 2 interfaces, single-crystal Si possesses one of the best known lattice thermal conductivity [1,2]. This exceptional heat conductance is critically important for Si device heat management and circuit reliability. However, most of the modern complementary metal-oxide-semiconductor (CMOS) platforms are no longer single-crystal Si wafers but rather thin layers of Si-on-insulator (SOI), ultrathin strained Si and SiGe heterostructures that are the foundation of SiGe bipolar transistors (HBTs), and high-mobility metal-oxide-semiconductor field-effective transistors (MOSFETs). Major properties of these Si-based nanostructures are very different from those of bulk c-Si. For example, thermal conductivity in ultrathin SOI layers, SiGe alloys, and Si/SiGe nanostructures could be reduced by more than an order of magnitude compared to that in c-Si [3-6], and heat dissipation has become an important issue for modern nanoscale electronic devices and circuits. Thus, the understanding and improvement of heat management in Si-based nanostructures is critically important for the evolution of microelectronic industry.On the other hand, many interesting applications of nanostructured Si (ns-Si) in photonic devices and CMOS-compatible light emitters were recently discussed [7][8][9][10][11]. These ns-Si materials and devices can be produced by electrochemical anodization (i.e., porous Si [12]), chemical vapor deposition (CVD) using thermal decomposition of SiH 4 [13-15], Si ion implantation into a SiO 2 matrix [16], and deposition of amorphous Si/SiO 2 layers followed by thermal crystallization [17][18][19]. These ns-Si materials and devices produce an efficient and tunable light emission in the near-infrared and visible spectral region [20,21]. Also, it has been shown that under photoexcitation with energy density >10 mJ/cm 2 , optical gain is possibly Silicon Nanocrystals: Fundamentals, Synthesis and Applications. Edited by Lorenzo Pavesi and Rasit Turan

(Invited) Axial Silicon-Germanium Nanowires: Properties and Device Applications

“…On considering the Raman measurements, we anticipate that under the applied laser excitation intensity of 10 2 -10 3 W/cm 2 the sample temperature increases, and such temperature increase can be detected by monitoring the Raman peak wavenumber and FWHM temperature dependencies (44)(45)(46). Generally, as temperature increases the Raman ECS Transactions, 98 (2) 13-28 (2020) peak shifts toward lower wavenumber due to thermal expansion and changes in the selfenergy of the vibrational mode.…”

Determining Strain, Chemical Composition, and Thermal Properties of Si/SiGe Nanostructures Via Raman Scattering Spectroscopy

“…In Si/SiGe CMs, we typically find that the volume fraction of SiGe is nearly twice that of Si/SiGe SLs, and it has been noted that inelastic scattering of phonons in Si/SiGe nanostructures with a diffuse interface also contributes to the reduction in the thermal conductivity (31). It was also reported that the temperature calculated according to Boltzmann statistics under a non-resonant excitation condition of the Ge-Ge phonon mode is consistently lower than that found for the Si-Ge and Si-Si modes (30). This discrepancy can be explained assuming that at the laser excitation wavelengths used, the Ge-Ge phonon mode has a resonant component, as pointed out in References 12, 32, and 33.…”

“…Typically, Raman scattering measurements are performed using an intense laser beam. While c-Si and c-Ge have a high thermal conductivity (κ ≈ 100 Wm -1 K -1 ), in compositionally disordered SiGe alloys and Si/SiGe nanostructures κ ≤ 10 W m -1 K -1 (30). Thus, a significant temperature increase of a sample might occur during Raman scattering measurements and it will affect the Raman peak position, width, and line shape.…”