Photoluminescence and I–V characteristics of ZnS grown on silicon nanoporous pillar array

Abstract

Silicon nanoporous pillar array (Si-NPA) is a silicon hierarchical structure with regularly patterned surface morphology. Through a heterogeneous reaction process, zinc sulfide nanocrystallites (nc-ZnS) were grown onto Si-NPA and a unique heterostructure of ZnS/Si-NPA was obtained. The formation of wurtzite nc-ZnS was proved by x-ray diffraction, and the average grain size was evaluated to be ∼18 nm. X-ray photoelectron spectroscopy disclosed that as-grown nc-ZnS was well separated from Si-NPA by a SiO2 thin layer of ∼1.3 nm. The photoluminescence (PL) spectrum of ZnS/Si-NPA showed that in addition to the two red PL bands peaked at ∼648 and ∼705 nm observed in Si-NPA, three other PL bands peaked at ∼365, ∼418, and ∼472 nm were observed and attributed to the PL from nc-ZnS. It was also demonstrated that as-prepared ZnS/Si-NPA heterostructure could exhibit good rectification characteristic featured by a high forward current density of ∼75 mA/cm2 at 2 V and high reverse breakdown voltage of ∼10 V. Our results indicated that ZnS/Si-NPA might be a valuable heterostructure nanosystem to be further probed for achieving enhanced optical and electrical properties.

Fabrication of Si/ZnS Radial Nanowire Heterojunction Arrays for White Light Emitting Devices on Si Substrates

“…The diode ideality factor of the present Si/ZnS nanowire radial heterojunction is superior to that reported for a similar structure fabricated with Si nanoporous pillar arrays (η ∼ 29.6). 19 However, the forward current density for our device is lower compared to that reported (75 mA/cm 2 ) in the above study. This may be due to relatively higher contact resistance of the AZO electrode compared to a pure metal electrode.…”

“…In the case of the nanowire heterojunction, the observed reverse saturation current density ( J 0 ) is only 0.006 mA cm –2 at a reverse bias of 3 V, which is fairly small in comparison to 0.09 mA cm –2 for the planar one. The diode ideality factor of the present Si/ZnS nanowire radial heterojunction is superior to that reported for a similar structure fabricated with Si nanoporous pillar arrays (η ∼ 29.6) . However, the forward current density for our device is lower compared to that reported (75 mA/cm 2 ) in the above study.…”

“…The fabricated Si/ZnS/AZO radial heterojunction device is schematically illustrated in Figure 4a. Since undoped ZnS film exhibits n-type conductivity with a carrier concentration of ∼10 16 /cm 3 , 19 the deposition of ZnS on p-Si nanowire leads to the formation of a core−shell-type, radial p−n heterojunction. In order to compare the electrical transport and optical characteristics of a SiNWs/ZnS radial heterojunction with the planar one, a planar thin-film heterojunction has also been fabricated.…”

“…Commonly, white light is produced by combining the emission from three LEDs (red, green, and blue) or by coating phosphors on blue indium gallium nitride (InGaN) LED chips. In recent years, several studies have been reported on Si/ZnS nanoheterostructures showing strong visible photoluminescence ranging from blue to red at room temperature, − indicating their potential in solid-state white light emitting devices. However, electrically driven light emitters using Si/ZnS heterojunctions are essential for application in LED devices.…”

The Surface Photovoltaic and Photoluminescent Evolution of a Silicon Nanoporous Pillar Array for Different Etching Times

“…[1−3] As a special type of the nc-Si/SiO 𝑥 nanostructures, the silicon nanoporous pillar array (Si-NPA) is a silicon hierarchical structure characterized by an array of micron-sized, quasi-identical and nanoporous silicon pillars with strong PL and broad-band light-absorption. [4] These morphological and structural features of Si-NPA make it an ideal template for preparing silicon-based nanosystems with enhanced physical properties, such as Ag/Si-NPA as an active layer in detecting low-concentration bio-molecules by surface-enhanced Raman scattering technique, [5] a carbon nanotube/Si-NPA nest array as the field emitter for obtaining high emission current density with low turn-on field, [6] metal oxides/Si-NPA as humidity sensing materials in realizing high sensitivity, short response/recovery times and small hysteresis, [7,8] wide-bandgap semiconductors/a Si-NPA nanoheterojunction array for getting excellent electrical rectification [9,10] and three-primarycolor PL, [10,11] and a GaN/Si nanoheterostructure array for the light emitting diode. [12,13] In nanosystems, Si-NPA plays the role of both a template for assembling the nanostructures and a contributor for obtaining specified physical properties.…”