Phononless radiative recombination of indirect excitons in a Si/Ge type-II quantum dot

Abstract

Phononless radiative recombination is observed in luminescence spectra of Ge quantum wells decorated by self-organized Stranski–Krastanow (S–K) dots grown on Si (100). External uniaxial tensile stress along [011] allows the discrimination of phonon-missing optical transitions. The phononless recombination is attributed to a dipole-allowed k diagonal Δ1-Γ25′ interband transition involving the hole in the Ge wetting layer and the electron in a Si quantum dot encompassed by large S–K dots. The weak oscillator strength of the phononless recombination is evidenced by its slow decay kinetics. The results indicate that low-lying broad band features due to S–K dots are also of phononless origins.

Germanium fin light-emitting diode

“…The dark currents of the Ge FinLED are increased substantially compared with those of the Si FinLED, but the observed ultralow dark current density of 1.86 Â 10 À5 (3.41 Â 10 À3 ) A/cm 2 at the reverse bias of 1(5) V is comparable to those reported as the record low dark currents. 20 The forward currents of the Ge Fin LED are reduced compared with those of the Si FinLED, presumably because of the type II band alignment 8 at the Ge fin/Si electrode interface. Nevertheless, the forward current density of the Ge Fin LED can be extremely high, exceeding the values of 3.40 Â 10 3 (4.62 Â 10 5 ) A/cm 2 at the bias of 1(5) V without a breakdown.…”

“…1,2 But, the only missing component to realize full monolithic integration in a conventional complementarymetal-oxide-semiconductor (CMOS) fabrication line is an electrically pumped laser diode (LD) composed of group IV materials, regardless of substantial progresses in light emissions from Si nano-structures. 3-7 Germanium (Ge) is a possible alternative candidate to Si, [8][9][10][11][12][13][14] since the conduction band energy of Ge at the C point is much lower than that of Si, and therefore, the properties of Ge are rather close to those of III-V compounds with the direct band gap. 10,11 In fact, the optical pumped laser 10 of Ge epitaxially grown on Si was achieved by the band engineering with a tensile strain and a donor doping at the L valleys.…”

Quantum Mechanics Design of Two Photon Processes Based Solar Cells

“…The large band discontinuities and the real-space indirect fundamental bandgap at the interface in type II Ge QDs embedded in Si are favorable, indeed, for the reduction of carrier recombination. For instance, electron inter-band recombination lifetime is extended to 1 μs in type II Ge QDs in Si (Fukatsu, 1997). Also up to 0.3 eV conduction band offset is possible in this system, which depends on the strain at the interface and the composition of Si spacers (Schaffler, 1997), hence it can be tuned by controlling the strain.…”

Miniband-related 1.4–1.8 μm luminescence of Ge/Si quantum dot superlattices

“…The broad QDSL band in the low-energy part of the PL spectrum is attributed to the optical transitions in the Ge/Si columns between holes, localized in the QDs, and electrons, tied to the interface by Coulomb interaction [8,9,[26][27][28][29][30][31][32]. At temperatures T £ 10 K the fine periodic structure of the QDSL band is distinctly observed.…”