Enhancement of photoluminescence of Ge/GeO ₂ core/shell nanoparticles

Abstract

Ge/GeO 2 core/shell nanoparticles embedded in an Al2O3 gate dielectrics matrix were fabricated. The core/shell nanoparticles consist of a single-crystal Ge core and a tiny GeO2 nanocrystallites shell. The high percentage of defects located at the shell surfaces and the grain boundaries between the Ge/GeO 2 nanocrystals or disorderly arranged areas in the GeO2 shell induce a significant phonon localization effect, which leads to enhanced radiative recombination and thus it enhances the photoluminescence intensity. We believe that the findings presented here provide physical insight and offer useful guidelines to controllably modify the optical properties of indirect semiconductors through defect engineering.

Effects of surface oxide formation on germanium nanowire band-edge photoluminescence

“…Selective Au etching 27 after NW growth was not used, to avoid possibly altering the sidewall surface characteristics of the wires. As previously reported, 28 the majority carrier (hole) concentration in these undoped Ge NWs is estimated to be about 10 14 $6.5 lm. Quantum confinement effects are expected to be negligible in these NWs because their diameter is larger than the exciton Bohr radius ($24 nm) of Ge.…”

“…[6][7][8][9][10] Other studies have mainly concerned visible PL from Ge nanocrystals embedded in various oxide matrices, and the role of the defects at the nanocrystal/ matrix interface or in the matrix itself. [11][12][13][14][15][16] In the case of Ge NWs, there are few reports of PL detected for band-to-band transitions in such nanowires, 17 due to the difficulty of detecting emission from unpassivated Ge NWs, which results from carrier trapping and nonradiative recombination. Among these, coherently strained Ge core/ SiGe shell nanowires exhibiting strong and bulk-like bandedge PL have been reported recently.…”

A Review on Ge Nanocrystals Embedded in SiO2 and High‐k Dielectrics

“…The annealing temperature with the largest memory window was 800 °C . The Ge nanoparticles show also a PL signal in the visible range, which was attributed either to interface defect centers or nanocrystal confined carrier recombination …”

“…Even larger memory windows of up to 6.4 V can be formed by using five storage layers. [111] The annealing temperature with the largest memory window was 800 C. [114] The Ge nanoparticles show also a PL signal in the visible range, which was attributed either to interface defect centers [122][123][124] or nanocrystal confined carrier recombination. [121]…”

Size and Shape Controlled Semiconductor Nanocrystals Synthesized by RF‐Sputtering Techniques for Electronic and Optoelectronic Applications

“…11) spectral range. However, also defects in the matrices [46,47], radiative transitions at the interfaces between nanocrystals and matrix [33][34][35][36] and GeO 2 interface defects [48] are discussed as possible origins, especially for luminescence bands near the high-energy peak. All spectra consist of two well distinguishable PL peaks at about 2.2 eV (low-energy peak) and 2.9 eV (high-energy peak).…”