Magnetic-field-enhanced quantum-cascade emission

Abstract

We have observed an enhancement of terahertz intersubband electroluminescence in a quantum cascade structure in the presence of a magnetic field applied normal to the epitaxial layers. At a field of B=7.2 T the emission efficiency doubles. This effect is attributed to the suppression of nonradiative Auger–intersubband transitions caused by Landau-quantization of the in-plane electron motion. The magnetic field dependence of the luminescence intensity shows strong oscillations. These magnetointersubband oscillations are caused by the modulation of the transition rate via resonant inter-Landau-level transfer.

Terahertz intersubband emission in strong magnetic fields

“…The increase of the lifetime of the upper state of the transition in a structure based on a diagonal transition, 9 as well as the suppression of a sequential tunneling current in a three-barrier, two-well heterostructure, 12 and the enhancement of the electroluminescence ͑EL͒ in a vertical transition 13 have also been observed by applying such a perpendicular magnetic field.…”

“…[9][10][11] In this paper we explore the magnetic limit at which the cyclotron energy ប c is larger than the intersubband transition energy E trans ; for our samples, this is the case at about 9.3 T for GaAs material system and 5.9 T for InGaAs material system ͑for hϭ16 meV͒. The increase of the lifetime of the upper state of the transition in a structure based on a diagonal transition, 9 as well as the suppression of a sequential tunneling current in a three-barrier, two-well heterostructure, 12 and the enhancement of the electroluminescence ͑EL͒ in a vertical transition 13 have also been observed by applying such a perpendicular magnetic field.…”

Self-consistent scattering theory of transport and output characteristics of quantum cascade lasers

“…͑1͒. The equations describing the rates dn i /dt in the collector region (iϭ1,2,3,5,7) are symmetric with those in the injector region (iϭ8, 10,11,13,15), and when the system reaches a steady state, the collector subbands population should equal those in injector subband. This implies that the injection rates on each side of the active region are equal.…”

Population-inversion and gain estimates for a semiconductor TASER

“…Sun and Khurgin [18] give the gain (in cm ) of a four-level infrared intersubband laser as (7) where volumetric population inversion (in cm ); refractive index; emission wavelength (in free space); full-width at half-maximum (FWHM) of the stimulated emission. Defining the quantum-well layer thickness as , then the volumetric charge densities can be converted to the sheet charge densities (in cm ) used in this work, thus giving (8) Taking the case of the 240 Å GaAs/20 Å Ga Al As design, and the room temperature data point in Fig. 7, then cm .…”

“…In particular, there has been a recent flurry of activity on both the theoretical [2]- [5] and experimental [6]- [8] fronts. In this vein, Soref et al [9] proposed a device design based on the philosophy of light-hole-to-heavy-hole intersubband transitions within a p-type SiGe/Si superlattice.…”