Fabrication and Photoluminescence Study of Large-Area Ordered and Size-Controlled GeSi Multi-quantum-well Nanopillar Arrays

Abstract

Large-area ordered GeSi multi-quantum-well nanopillar array (MQW-NPA) samples with different nanopillar lateral sizes (270, 120, and 70 nm) are fabricated by a cost-effective and scalable dry-etching process in combination with nanosphere lithography technique. A significant enhancement in photoluminescence (PL) intensity has been observed in the GeSi MQW-NPA samples compared with the as-grown GeSi MQW one. Nanopillar samples with different lateral sizes show different enhancements in PL intensity. The enhancements are analyzed quantitatively and attributed to three factors. One is the antireflection of the nanopillar structures. Another is an enhanced extraction in nanopillar arrays at the emission wavelength. Thirdly, the GeSi quantum wells in close proximity to the substrates would have more contribution to the PL than before etching. Our results show that all the three factors should be taken into account in designing and fabricating surface microstructures of GeSi MQW materials in order to improve their optical properties.

Composition analysis and transition energies of ultrathin Sn-rich GeSn quantum wells

“…While we included PL data for series 2 obtained from a different measurement setup in the Supplemental Material [27], we restrict the following results and discussion to data obtained from series 3. An increase in PL signal intensity in structured nanocolumn samples compared to the unstructured samples has been observed previously [49] and was attributed to an increase in absorption of the incident light due to the antireflective properties of the patterned surface as well as an increase in the effective penetration depth of the incident laser light.…”

A self-consistent numerical approach for characterizing the band structures and gain spectrum of tensile-strained and n+-doped Ge/GeSi quantum wells

“…where Ω is the damping factor, ρ [k+1] (z) is the damped charge distribution which will be used to replace ρ [k+1] (z) in equation (19) at iteration step (k + 1). The charge distribution of each step will be damped by adding a part of the results of its history from the last iteration.…”

“…So far, CSE in GeSi QWs has not been sufficiently investigated. Jiang et al found that the wavelength of the peak optical gain was related to the carrier density which indicates a shift in energy level was introduced by an extra carrier [19]. Pizzi et al ruled out the attempt of doping in the barriers because of the severe electrostatic potential that will break the confinement potential [20].…”

“…In fact, the electrostatic potential plays an important role on the subband energy levels along with the carrier occupation at such a high charge density. Previous works have noted that the electrostatic potential was crucial in n + -doped GeSi QW [19][20][21], but detailed analysis was left for further discussion. Nevertheless, the CSE on the optical gain in the Ge/GeSi QWs has rarely been reported.…”

Controllable Fabrication of Non-Close-Packed Colloidal Nanoparticle Arrays by Ion Beam Etching

“…Polystyrene (PS) nanospheres have been attracting great attention from several research fields due to their ability for fabricating novel nanomaterials and nanostructures, such as ordered nanowire arrays [ 1 – 3 ], nanopillar arrays [ 4 , 5 ], nanohole arrays [ 6 , 7 ], nanodot arrays [ 8 ], core/shell composite materials [ 9 , 10 ], nanomesh [ 11 , 12 ], and magnetic quantum dots [ 13 ]. Particularly, nanosphere lithography has been one of the most popular research hotspots in designing the ordered nanostructure arrays since it takes the advantages of simpler process and lower cost.…”