Picosecond Optical Measurements of Band-to-Band Auger Recombination of High-Density Plasmas in Germanium

Auston, D. H.; Shank, C. V.; LeFur, P.

doi:10.1103/physrevlett.35.1022

Cited by 102 publications

(26 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The third term refers to free carrier diffusion with ambipolar diffusion coefficient D = 67 cm 2 /s, 25 the fourth term to radiative recombination with lifetime τ = 100 µs, 26 and the final term to Auger recombination with Auger coefficient A = 2 × 10 -31 cm 6 /s. 27,28 This pair of coupled differential equations was solved numerically using a time-and-spacediscreet pulse propagation simulation, with consideration given to the profile of the micropulses in time and space (assumed to be Gaussian in both cases), multiple reflections inside the sample using the usual Fresnel coefficients, and to the accumulation of carriers between micropulses. The simulation code was verified for accuracy by comparison with simpler analytical models.…”

Section: Methodsmentioning

confidence: 99%

Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation

et al. 2011

View full text Add to dashboard Cite

We report wavelength-and intensity-dependent transmission measurements of intense mid-infrared radiation from the Vanderbilt Free Electron Laser in single-crystal Ge(100) in the wavelength range of 2.8-5.2 μm. This range accesses both the direct and indirect energy gaps in Ge, requiring in each case either two or three photons (2PA or 3PA) for absorption. Large changes in the multi-photon absorption rate are seen at the direct-to-indirect and 2PA-to-3PA transitions. Photon interactions are dominated by free carrier absorption (FCA), primarily due to holes. The entire absorption process is modeled with the two-and three-photon absorption coefficients (β and γ) as fitting parameters.Using newly measured values of the low-intensity FCA cross-sections, we find a best fit to the data at 2.8 µm that is in agreement with theory and previous measurements. We report a ratio of 175 for β across the direct-to-indirect transition, and a ratio of 5 across the same transition for γ. These ratios are independent of systematic variations in free carrier cross-sections and beam diameter. Receipt

show abstract

Section: Methodsmentioning

confidence: 99%

Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation

et al. 2011

View full text Add to dashboard Cite

show abstract

“…Like in conventional semiconductors, strong optical excitation results in a population-inverted state [15][16][17][18][19][20]. On the other hand, photo-generated electron-hole pairs in a conventional semiconductor typically relax by Auger recombination [21][22][23][24], a process that is strongly suppressed in photo-excited graphene due to the abence of occupied states at the bottom of the conduction band. Hence, in contrast to conventional semiconductors, primary thermalization events in graphene are dominated by impact ionization [25][26][27][28], where the excess energy of the photo-excited electron is used to generate additional electron-hole pairs.…”

Section: Introductionmentioning

confidence: 99%

Probing carrier dynamics in photo-excited graphene with time-resolved ARPES

Gierz

2017

Journal of Electron Spectroscopy and Related Phenomena

View full text Add to dashboard Cite

The dynamics of photo-generated electron-hole pairs in solids are dictated by many-body interactions such as electron-electron and electron-phonon scattering. Hence, understanding and controlling these scattering channels is crucial for many optoelectronic applications, ranging from light harvesting to optical amplification. Here we measure the formation and relaxation of the photo-generated non-thermal carrier distribution in monolayer graphene with time-and angleresolved photoemission spectroscopy. Using sub 10fs pulses we identify impact ionization as the primary scattering channel, which dominates the dynamics for the first 25fs after photo-excitation.Auger recombination is found to set in once the carriers have accumulated at the Dirac point with time scales between 100 and 250fs, depending on the number of non-thermal carriers. Our observations help in gauging graphene's potential as a solar cell and TeraHertz lasing material.

show abstract

“…However, previous studies on the ultrafast spectroscopy of Ge showed inconsistent results. [8][9][10][11][12][13] For example, instead of observing optical gain, in Refs. 8 and 9, a significant decrease in transmittance at 1550 nm was observed upon ultrafast pulse pumping with photon energy well above the direct gap of Ge ($360 meV higher).…”

mentioning

confidence: 99%

“…U intervalley scattering absorption, which has been observed recently in the infrared absorption spectra of 0.25% tensile strained n þ Ge films 14 yet never reported in n þ bulk Ge. 8 On the other hand, pressure-dependent ab initio calculation shows that the contributions of various phonons to the intervalley scattering are quite dependent on the conduction band energy separation. 25 Further combination of tensile strain and phonon engineering with nanostructures 26 may help to achieve this goal.…”

mentioning

confidence: 99%

Large inherent optical gain from the direct gap transition of Ge thin films

Wang

Kimerling

Michel

et al. 2013

Applied Physics Letters

View full text Add to dashboard Cite

The recent demonstration of Ge-on-Si diode lasers renews the interest in the unique carrier dynamics of Ge involving both direct (Γ) and indirect (L) valleys. Here, we report a large inherent direct gap optical gain ≥1300 cm−1 at room temperature from both tensile-strained n+ Ge-on-Si films and intrinsic Ge-on-insulator using femtosecond transmittance spectroscopy captured before direct-to-indirect valley scattering. This inherent direct gap gain is comparable to III-V semiconductors. For n+ Ge, this transient gain is ∼25× larger than its steady state gain, suggesting that reducing Γ→L or enhancing L→Γ intervalley scattering may significantly increase the optical gain of Ge lasers.

show abstract

Picosecond Optical Measurements of Band-to-Band Auger Recombination of High-Density Plasmas in Germanium

Cited by 102 publications

References 12 publications

Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation

Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation

Probing carrier dynamics in photo-excited graphene with time-resolved ARPES

Large inherent optical gain from the direct gap transition of Ge thin films

Contact Info

Product

Resources

About