Optimization in the nanostructural evolution of hydrogenated silicon germanium thin film in RF-PECVD

Das, Debajyoti; Dey, Amaresh

doi:10.1016/j.physe.2019.02.024

Cited by 12 publications

(3 citation statements)

References 49 publications

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“…However, later it increased sharply at F = 20 sccm. The average grain size ( d ) was estimated using the full width at half-maximum (FWHM, β) of the XRD peaks, following Scherrer’s formula , and is presented in Figure c. Corresponding to the increasing PH 3 flow rate ( F ), the <111>-oriented nanocrystallites reduced in size monotonically from 18.93 to 12.54 nm.…”

Section: Resultsmentioning

confidence: 99%

“…The microstructure factor, R, an indicator of the fraction of polyhydride components in the material, is defined as and the surface passivation index (S), attributed to the proportional atomic H bonded as Si–H–Si cluster configuration on the surface of the nanocrystals, is defined as where I is the integrated area under each component. With increased dopant in the network, the microstructure factor reduced gradually and the surface passivation index increased, as presented in Figure b.…”

Section: Resultsmentioning

confidence: 99%

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Superior Phosphorous Doping in Nanocrystalline Silicon Thin Films and Their Application as Emitter Layers in Silicon Heterojunction Solar Cells

Das

Patra

2023

Energy Fuels

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Phosphorous doping in the nc-Si network induces gradually reduced crystallinity; however, preferential growth along <220>-oriented crystallites promotes the columnar-like growth morphology. At optimum doping, substitution by donor P+-atoms in the c-Si lattice contributes surplus free electrons and high carrier mobility, resulting in superior electrical conductivity in the n-nc-Si network. An elevated doping leads to incorporating elemental P0 atoms in the interstitial position or forming P–Si–H clusters and generating voids between the crystalline columns. Segregation of defects contributes to decreasing carrier mobility and reducing conductivity after diminishing crystallinity and narrowing the optical band gap. By precisely controlling the growth at 250 °C and efficient electrically active doping by P+-atoms, n-nc-Si thin films with superior dark conductivity (∼101 S cm–1) are produced in which the percolation of charge carriers through the crystalline columns could facilitate stacked-layer devices. The optimum n-nc-Si thin films are used as the emitter layers in n-nc-Si/p-c-Si heterojunction solar cells (HJSCs). Furthermore, an ultrathin a-Si:H buffer layer on the p-c-Si minimizes the junction carrier recombination loss, and subsequent postdeposition short-time H-plasma treatment (PSHPT) ensures seeds for superior nanocrystallization in the n-nc-Si emitter layer. The n-nc-Si/(PSHPT)i-nc-Si(buffer layer)/p-c-Si HJSC delivers a PV conversion efficiency, η ∼12.35%, via a reasonable fill factor of ∼0.647 and sensible JSC of ∼32.75 mA cm–2. Further improvement in the PV performance could be possible using suitably thinner p-c-Si wafers, harmonizing with the effective carrier diffusion length, and fabricating a high-quality passivation structure on the backside.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Superior Phosphorous Doping in Nanocrystalline Silicon Thin Films and Their Application as Emitter Layers in Silicon Heterojunction Solar Cells

Das

Patra

2023

Energy Fuels

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“…Furthermore, for the film prepared at T S = 170 °C, the Si–H stretching mode vibration bands are deconvoluted in three components, namely, SiH mono-hydride stretching (∼2000 cm –1 ), Si–H–Si plate-like stretching (∼2050 cm –1 ), and SiH 2 di-hydrate stretching (∼2100 cm –1 ), as presented in Figure h. The relative strengths of the SiH 2 and Si–H–Si platelet-like stretching modes in the matrix are determined by the microstructure factor ( R ) and the surface passivation index ( S ), respectively, and these are defined as , where I represents the integrated intensity of the corresponding peak. The SiH 2 mode generally shows the existence of voids, defects, and the dangling bonds.…”

Section: Resultsmentioning

confidence: 99%

Studies on the Impedance Characteristics, Dielectric Relaxation, and ac Conductivity in Silicon Oxycarbide (SiO_xC_y:H) Films at the Amorphous-to-Nanocrystalline Transition Zone

Shyam

Das

2022

ACS Appl. Electron. Mater.

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The impedance characteristics and ac conductivity behavior of the silicon oxy-carbide (SiO x C y :H) network have been investigated during its transition from an amorphous dominated to a crystalline populated structure, grown by varying only the growth temperature (T S) from 160 to 180 °C. At elevated T S, the Si nanocrystals (Si-ncs) increased in size and number density, with corresponding elevation in crystallinity from 28 to 45%. Two distinct dielectric relaxations for the individual a-SiO x C y :H and nc-Si components were identified in the low-frequency and high-frequency zones, respectively, for the film deposited at higher T S (180 °C). In contrast, for the lower T S (160 °C)-grown film, a significant fraction of the ultra-nanocrystalline (unc-Si) component contributed only one consolidated relaxation peak at a moderate frequency. The scaling measurements of the imaginary part of impedance (−Z Im) revealed two distinct physical events for a-SiO x C y :H and nc-Si, both being temperature scale-independent. The activation energy of relaxation is low for the ordered nc-Si component and high for the disordered a-SiO x C y :H matrix. According to the Bode plot analysis, the presence of several defects in the grain boundary contributed a poor carrier lifetime to the nc-Si component, while the a-SiO x C y :H matrix with lesser defects had a longer carrier lifetime. An equivalent circuit model formed by parallel resistors and constant phase elements (R||CPE), following Nyquist plot analysis, demonstrated an intense association between the microstructural and charge carrier characteristics. The temperature-dependent ac-conductivity behavior of the mixed-phase material is well explained by the nonoverlapping small polaron tunneling model, at two individual stages across a transition from an amorphous to crystalline configuration around a small span of growth temperature.

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Optimal H2-dilution playing key role in accomplishing significant nanocrystallinity with both Si and Ge moieties in SiGe nanocomposite thin film network

Dey

Das

2022

Applied Surface Science

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Optimization in the nanostructural evolution of hydrogenated silicon germanium thin film in RF-PECVD

Cited by 12 publications

References 49 publications

Superior Phosphorous Doping in Nanocrystalline Silicon Thin Films and Their Application as Emitter Layers in Silicon Heterojunction Solar Cells

Superior Phosphorous Doping in Nanocrystalline Silicon Thin Films and Their Application as Emitter Layers in Silicon Heterojunction Solar Cells

Studies on the Impedance Characteristics, Dielectric Relaxation, and ac Conductivity in Silicon Oxycarbide (SiO_xC_y:H) Films at the Amorphous-to-Nanocrystalline Transition Zone

Optimal H2-dilution playing key role in accomplishing significant nanocrystallinity with both Si and Ge moieties in SiGe nanocomposite thin film network

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Optimization in the nanostructural evolution of hydrogenated silicon germanium thin film in RF-PECVD

Cited by 12 publications

References 49 publications

Superior Phosphorous Doping in Nanocrystalline Silicon Thin Films and Their Application as Emitter Layers in Silicon Heterojunction Solar Cells

Superior Phosphorous Doping in Nanocrystalline Silicon Thin Films and Their Application as Emitter Layers in Silicon Heterojunction Solar Cells

Studies on the Impedance Characteristics, Dielectric Relaxation, and ac Conductivity in Silicon Oxycarbide (SiOxCy:H) Films at the Amorphous-to-Nanocrystalline Transition Zone

Optimal H2-dilution playing key role in accomplishing significant nanocrystallinity with both Si and Ge moieties in SiGe nanocomposite thin film network

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Product

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Studies on the Impedance Characteristics, Dielectric Relaxation, and ac Conductivity in Silicon Oxycarbide (SiO_xC_y:H) Films at the Amorphous-to-Nanocrystalline Transition Zone