Trapping of carriers in single quantum wells with different configurations of the confinement layers

Abstract

This paper reports detailed experimental studies of low-temperature carrier trapping in GaAs/A1"Gal "As single quantum wells with 5 nm and 1.2 nm thickness, respectively, with different confinement structures. Trapping efficiency and trapping dynamics are studied by means of photoluminescence, photoluminescence excitation spectroscopy, and picosecond luminescence spectroscopy. %'e obtain trapping efficiencies of about 40% for both the single quantum wells without additional confinement and separate-confinement-heterostructure quantum wells. The percentage of trapped carriers increases to about 60%%uo to 80% for quantum wells cladded by gradedindex separate-confinement heterostructures with parabolic band-gap profile. The maximum trapping eSciency of about 100% has been observed for a separate-confinement heterostructure with a linear band-gap profile. Interlayer well width fluctuations are found to be unimportant for the trapping behavior in our samples. Trapping times are appreciably shorter than the rise times of the quantum well photoluminescence, which are between 60 and 100 ps for the different structures.Surface recombination in the 0.2-p, m-thick Al"Gal "As cladding layer does not reduce the trapping efficiency of the single quantum well without additional confinement compared with the separateconfinement heterostructure. An effective trapping area with about 80 nm width can be deduced on the basis of these results for the quantum-well structures with ungraded cladding layers.

Early stages of continuous wave experiments on cavity‐polaritons

“…8, assuming that all the excited carriers are evenly shared between the six quantum wells in the cavity. This last assumption will tend to overestimate the electron-hole pair density, as the capture efficiency is probably less than 100% [28]. The measurements could be well fitted by the standard screening function [29]:…”

Quantum-well capture and interwell transport in semiconductor active layers

“…at different temperatures, carrier densities, well and barrier widths, etc). These include static [10,11,38] and time-resolved [7,[12][13][14][15][16][17][18][19] photoluminescence, pump-probe spectroscopy [20][21][22] and modulation response measurements [23][24][25][26]. The estimated values for the capture lifetime reported in these works vary over a wide range, from several hundreds of femtoseconds to several tens of picoseconds, which is only partly justified by the differences among the samples studied.…”

“…A remarkable result of these early studies was the prediction of an oscillatory dependence of the capture rate on the QW width. The large body of experimental work that followed [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], based on several different techniques, found measured values for the capture lifetime varying over a wide range, from a fraction to tens of picoseconds, depending on the experimental conditions. Similarly, the predicted oscillations with well width were only observed under appropriate conditions [10,18,21], most notably in the low carrier density regime, where the lifetime broadening of the delocalized single-particle states is small.…”

A new approach to determine radiative recombination lifetime in quantum well solar cells

“…A detailed review of the fundamentals of recombination lifetime modelling has been performed by Pratt et al [4]. Since then many researchers have conducted calculations and experimentation for various electronic devices [5][6][7][8][9][10][11][12][13]15,17]. Our choice to study radiative recombination is seen through Barnham's original work [1].…”