Effect of Doping with Shallow Donors on Radiative and Nonradiative Relaxation in Silicon Nanocrystals: Ab Initio Study

Abstract

Electronic structures of 1−2 nm in diameter hydrogen-passivated silicon nanocrystals and rates of the radiative interband transitions and Auger recombination were calculated on the basis of first-principles (DFT/TDDFT) methods for the nanocrystals doped with a single centrally located phosphorus or lithium atom. We have found a significant increase of the radiative recombination rates caused by the nanocrystals' doping at room temperature. For the Pdoped crystallites, this effect takes place at zero temperature as well, while the Li-doped crystallites (at least, some of them) demonstrate strong temperature dependence of the recombination rates, which drastically drop as the temperature decreases. The rates of the Auger recombination in the nanocrystals with Li, on the whole, turn out to be of the same order of magnitude as in the undoped nanocrystals. On the contrary, in the P-doped nanocrystals, the Auger process becomes considerably slower.

Exciton-Photon Interactions in Semiconductor Nanocrystals: Radiative Transitions, Non-Radiative Processes and Environment Effects

“…Usually, the Auger recombination is an efficient process that can "shunt" other photonassisted processes such as light emission or multiple exciton generation. For instance, in Si crystallites, the Auger rates can be sufficiently high, as the measurements [133,134] and calculations [106,[135][136][137][138] show. Therefore, suppression of the Auger process is an important practical problem.…”

“…It was revealed that doping of Si nanocrystals with P or Li is (under certain conditions) capable of improving their emittance [84,87,89,118]. In particular, the performed calculations [87,99,106,107] show that doping with P or Li can essentially increase the radiative transition rates.…”

“…Many methods have been proposed to increase their emissivity, such as doping with shallow impurities [83][84][85][86][87][88][89], growth in different matrices [90,91], plasma [92,93], and colloidal solutions [94][95][96][97][98]. As a result, numerous theoretical predictions and experimental observations of enhanced PL intensity [83,84,87,88], radiative recombination rates [89,[99][100][101][102][103][104][105][106][107] and quantum efficiency of photon generation [108] have been reported.…”

Exciton-photon interactions in semiconductor nanocrystals: {radiative transitions, non-radiative processes,} and environment effects

“…It was revealed that doping of Si nanocrystals with P or Li is (under certain conditions) capable of improving their emittance 85,88,90,119 . In particular, the performed calculations 88,100,107,108 show that doping with P or Li can essentially increase the radiative transition rates.…”

“…Many methods have been proposed to increase their emissivity, such as doping with shallow impurities [84][85][86][87][88][89][90] , growth in different matrices 91,92 , plasma 93,94 , and colloidal solutions [95][96][97][98][99] . As a result, numerous theoretical predictions and experimental observations of enhanced PL intensity 84,85,88,89 , radiative recombination rates 90,[100][101][102][103][104][105][106][107][108] and quantum efficiency of photon generation 109 have been reported.…”