Auger recombination dynamics of lead salts under picosecond free-electron-laser excitation

Abstract

Pump-probe transmission experiments have been performed on PbSe above the fundamental absorption edge near 4 m in the temperature range 30 to 300 K, using the Dutch ps free-electron laser. For temperatures below 200 K and carrier densities above the threshold for stimulated emission, stimulated recombination represents the most efficient recombination mechanism with relatively fast kinetics in the 50-100-ps regime, in good agreement with earlier reports of photoluminescent emission. Above this temperature Auger recombination dominates, and the Auger coefficient C is determined from the pump-probe decay curves. In the lowtemperature regime the Auger coefficient is determined from the decay curves at times beyond 100 ps. The Auger coefficient is approximately constant ͑with a value of about 8ϫ10 Ϫ28 cm 6 s Ϫ1) between 300 and 70 K, and then drops a value of about 1ϫ10 Ϫ28 cm 6 s Ϫ1 at 30 K, in good agreement with the theory for nonparabolic near-mirror bands and nondegenerate statistics. It is found that C for PbSe is between one and two orders of magnitude lower than for Hg 1Ϫx Cd x Te of comparable band gap. ͓S0163-1829͑98͒07243-9͔

Silicon as a model ion trap: Time domain measurements of donor Rydberg states

“…In this technique, described in detail elsewhere, a strong pump pulse causes bleaching of the absorption measured by the weak probe pulse, the recovery of which is then measured as a function of the delay between the two (18,19). The samples investigated were float-zone-grown Si wafers of thickness Ϸ200 m and doped with P or As to donor concentrations of N0 ϳ 2 ϫ 10 21 m Ϫ3 .…”

“…The latter include random strain fields induced by impurities and/or dislocations (16,17), and other fluctuations in the donor environment caused by chemical impurities and different isotopes in the natural composition of Si with differing nuclear moment (3-5). Time-domain methods such as ours (18,19) can directly measure the relaxation without any convolution, but require a short-pulse laser, in our case, a far-infrared free-electron laser. In addition, and much more importantly for future work, these methods open up the prospect of laser control of impurity states, in precise analogy with the breakthrough that pulsed paramagnetic and nuclear…”

Interwell relaxation times inp−Si∕SiGeasymmetric quantum well structures: Role of interface roughness

“…Each macropulse consists of a train of micropulses of duration ∼10 ps and 25 MHz repetition rate. A pump-probe technique (or transient bleaching technique) in which the FELIX beam is split into pump, probe and reference beams was used [15]. The samples were mounted in vacuum on the cold finger of a liquid helium continuous flow cryostat, with temperature variable from 4.2 K to 300 K. In order to access the HH-HH transitions it was necessary to pump and probe at oblique incidence, enabling the polarization selection rule E parallel to the growth direction.…”

Mid-Infrared Surface-Emitting Two Dimensional Photonic Crystal Semiconductor Lasers

“…Lead salt or IV-VI semiconductor system has been used as a major material source for mid-IR diode lasers for a long time, because of its energy bandgap covering the wavelength region from 3 to 30 m (Preier, 1990;Ishida & Fujiasyu, 2003;Tacke M. , 2000) and also its near two orders of magnitude lower non-radiative Auger recombination rates as compared to other conventional narrow band gap semiconductors (Findlay, et al, 1998). In this section, the realization of surface emitting photonic crystal lasers based on the lead salt compounds is described.…”