Radiatively Dominated Charge Carrier Recombination in Black Phosphorus

Abstract

We show that black phosphorus is a highly efficient infrared emitter. To study the carrier dynamics, excess electron-hole pairs were generated in bulk black phosphorus by irradiation with 3 MeV electron pulses. The transient microwave conductivity due to excess charges was measured as a function of time for different initial charge densities at temperatures in the range 203-373 K. A new global analysis scheme, including the treatment of intrinsic carriers is provided, which shows that the recombination dynamics in black phosphorus, a low bandgap semiconductor, is strongly influenced by the presence of intrinsic carriers. The temperature dependence of the charge mobility and charge carrier decay via second-order radiative recombination is obtained from modeling of the experimental data. The combined electron and hole mobility was found to increase with temperature up to 250 K and decrease above that. Auger recombination is negligible for the studied densities of excess electron-hole pairs up to 2.5×10 17 cm -3 . For this density the major fraction of the excess electrons and holes undergoes radiative recombination. It is further inferred that for excess charge densities of the order of 10 18 cm -3 electrons and holes recombine with near unity radiative yield. The latter offers promising prospects for use of black phosphorus as efficient mid infrared emitter in devices.

Charge Mobility and Recombination Mechanisms in Tellurium van der Waals Solid

“…In the present investigation, we provide insights into temperature-dependent intrinsic charge carrier mobility and decay mechanisms in trigonal Te with varying charge carrier density, building up on our earlier results on other van der Waals materials. 9,25 Quantitative analysis of our experimental observations reveals the characteristics of charge carrier mobility and recombination in the quasi-1D atomic chains of Te in bulk, laying the basis for further investigations of exfoliated Te. The high mobility and near-unity quantum yield (QY) make Te of interest for nanoelectronics and optoelectronics.…”

“…The microwave conductivity studies were performed at frequencies in the range of the K a band (27–38 GHz), similar to our previous studies. 9,25 Uniform densities of excess electrons and holes were generated by irradiation with 3 MeV electron pulses from a van de Graaff accelerator, along with Bremsstrahlung irradiation, which was produced by retarding the electron pulses by a 2 mm lead (Pb) sheet. The high-energy Bremsstrahlung photons generate electron–hole pairs along their paths through the sample.…”

Mobility and Decay Dynamics of Charge Carriers in One-Dimensional Selenium van der Waals Solid

“…To study the dynamics of excess charge carriers, the Se powder was introduced into a microwave conductivity measurement cell with dimensions suitable for frequencies in the K a band (27–38 GHz), similar to our previous studies. 24 High-energy (3 MeV) electron pulses from a van de Graaff accelerator were used to generate excess electrons and holes in the sample. The high-energy electrons pass through the sample and lose energy by generating a close to uniform distribution of electron–hole pairs along their tracks without inducing net charging in the sample.…”

“…The radiation dose in the Se sample, D Se , was obtained from a reference measurement on benzene (Bz) according to D Se = D Bz ( N e,Se ρ Se M Bz / N e,Bz ρ Bz M Se ), where N e , ρ, and M are respectively the number of electrons per atom/molecule, mass density, and atomic/molecular mass for Se or Bz. 24 , 26 The electron–hole pair formation energy, E p , was estimated from the empirical formula provided by Alig et al, 27 which is given by E p = 2.73 E g + b , where b = 0.5 eV and E g = 1.9 eV, 18 the band gap of trigonal Se. The density of generated electron–hole pairs is given by the ratio D Se / E p .…”

“…The aim of the present study is to provide insight into the mobility and charge decay dynamics via trapping or recombination in trigonal Se at varying charge carrier density, similar to our previous work on 2D black phosphorus. 24 Possible negative effects of backscattering of charges at the ends of Se chains on the mobility are discussed, using the theoretical model of Prins et al 25 …”