Optical transitions to above-barrier quasibound states in asymmetric semiconductor heterostructures

Abstract

An asymmetric semiconductor electron wave Fabry–Perot interference filter has been designed with two above-barrier quasibound states for optical transitions. The upper state was designed to have a spatial confinement lifetime greater than three times that of the lower state (which was designed to be less than 100 fs). Such lifetime ratios and magnitudes, which are nearly impossible for below-barrier states, satisfy the criteria required for achieving population inversion. Furthermore, the transitions were designed to have large dipole matrix elements. Absorption measurements at multiple temperatures were used to demonstrate the first bound-to-quasibound transitions in an asymmetric structure. The experimental energies and dipole matrix elements are in agreement with calculated values. This type of structure could represent the basis for a new room-temperature infrared semiconductor laser.

Electron transport process in quantum cascade intersubband semiconductor lasers

“…The state lifetimes of bound states are infinite, while those of quasibound states are usually of the order of picoseconds or femtoseconds. However, in QW structures an inversion of lifetimes corresponding to their energy subbands can happen 17 as is the case with the TQWCL. 8 Figure 2 shows electron state lifetimes at each energy subband which appears in the active region of TQWCL under chosen applied biases.…”

The quasibound state model for self-consistent characteristics of semiconductor intersubband devices

“…Nonlinear photonic devices, such as nonlinear directional couplers [10] are based on this phenomenon. Other intersubband devices are electron energy filters [11], resonant tunneling transistors [12], hot-electron spectrometers [13], and electron diffraction grating switches [14,15].…”

Quantum-well infrared photodetector structure synthesis: methodology and experimental verification

“…With this in mind, the central part of the GaAs well in the QWIP structure is doped at 1.0 10 cm . Assuming complete ionization of donors, the Fermi energy is calculated from the charge neutrality condition , where is the ionized donor sheet-density and is the two-dimensional subband population [27]. For the present calculation, complete .…”