Effects of P doping on photoluminescence of Si1−xGex alloy nanocrystals embedded in SiO2 matrices: Improvement and degradation of luminescence efficiency

Abstract

The effects of P doping on photoluminescence ͑PL͒ properties of Si 1Ϫx Ge x alloy nanocrystals (nc-Si 1Ϫx Ge x) in SiO 2 thin films were studied. P doping drastically decreases the electron spin resonance ͑ESR͒ signals that are assigned to the Si and Ge dangling bonds at the interfaces between nc-Si 1Ϫx Ge x and SiO 2 matrices ͑Si and Ge P b centers͒. With increasing P concentration, the signal from the Ge P b centers are first quenched, and then the signal from the Si P b centers start to be quenched. The quenching of the ESR signals is accompanied by a drastic enhancement of the PL intensity. The PL intensity has a maximum at a certain P concentration, which depends on the Si:Ge ratio. By further increasing the P concentration, the PL intensity becomes weaker. In this P concentration range, optical absorption emerges due to the intravalley transition of free electrons generated by the P doping. The observation of the free-electron absorption provides direct evidence that carriers in nanometer-sized Si 1Ϫx Ge x alloy crystals can be controlled by impurity doping.

Crystallization of Amorphous Si0.6Ge0.4 Nanoparticles Embedded in SiO2: Crystallinity Versus Compositional Stability

“…[1][2][3][4][5][6][7] The formation of nanocrystals has been reported using various approaches, e.g., ion implantation of Si or Ge in SiO 2 , [8][9][10][11] e-beam evaporation, 12 co-sputtering deposition of Si and/or Ge and SiO 2 , [13][14][15][16] and plasma-enhanced chemical vapor deposition. 17 These procedures usually end with an annealing step, necessary to form the nanocrystals, carried out at temperatures of 1000°C or higher and for times of around 1 h, conditions which often represent a high thermal budget.…”

Effect of As doping on the photoluminescence of nanocrystalline 74Ge embedded in SiO2 matrix

“…At room temperature, the P b centers act as a non-radiative recombination center, therefore decreasing the band-edge luminescence efficiency. Therefore, by decreasing the density of P b centers, the intensity of PL can be enhanced in P doping nc-Si or nc-SiGe [7,22,25]. It is the same case for the increasing of PL in As-doped nc-Ge.…”

Enhanced optical properties of Si1−xGex alloy nanocrystals in a planar microcavity

“…A multitarget sputtering apparatus was used to deposit multilayer films. [6][7][8][9][10] The layers of Bragg reflectors were deposited by alternately operating Si or SiO 2 sputtering guns, while active layers were deposited by operating Si, Ge, and SiO 2 guns simultaneously ͑in the case of nc-Si, Si, and SiO 2 guns͒. The sputtering rate of each gun was independently controlled by adjusting the sputtering power and the distance between sputtering targets and substrates.…”

“…[1][2][3][4][5][6] The tuning range can be expanded by Si 1Ϫx Ge x alloy formation, because the band gap ͑luminescence͒ energy of nanometer-sized Si 1Ϫx Ge x alloy crystals (nc-Si 1Ϫx Ge x ) changes from the widened bandgap of nc-Si to that of nc-Ge depending on x. [7][8][9][10] The wide tunability of PL peak energy prompts great interest in the development of Si-based light-emitting devices.…”