Negative activation energy and dielectric signatures of excitons and excitonic Mott transitions in quantum confined laser structures

Abstract

Mostly, optical spectroscopies are used to investigate the physics of excitons, whereas their electrical evidences are hardly explored. Here, we examined a forward bias activated differential capacitance response of GaInP/AlGaInP based multi-quantum well laser diodes to trace the presence of excitons using electrical measurements. Occurrence of "negative activation energy" after light emission is understood as thermodynamical signature of steady state excitonic population under intermediate range of carrier injections. Similar corroborative results are also observed in an InGaAs/GaAs quantum dot laser structure grown by molecular beam epitaxy. With increasing biases, the measured differential capacitance response slowly vanishes. This represents gradual Mott transition of an excitonic phase into an electron-hole plasma in a GaInP/AlGaInP laser diode. This is further substantiated by more and more exponentially looking shapes of high energy tails in electroluminescence spectra with increasing forward bias, which originates from a growing non-degenerate population of free electrons and holes. Such an experimental correlation between electrical and optical properties of excitons can be used to advance the next generation excitonic devices. Published by AIP Publishing. [http://dx

Explorations on the continuous oxidation kinetics of diesel PM from heavy-duty vehicles using a single ramp rate method

“…al [28] summarized large amounts of elementary reactions, with the conclusion that the apparent activation energy was negative for the elementary reaction in a narrow temperature range. Also, the abnormal phenomenon in chemical reactions was reported in other chemical reaction process [29][30][31].…”

Experimental evidences of quantum confined 2D indirect excitons in single barrier GaAs/AlAs/GaAs heterostructure using photocapacitance at room temperature

“…Lately, we have reported 7 how a thermodynamic population of dipolar excitons in quantum confined laser diodes can respond to steady state differential capacitance measurements and shift towards higher frequencies with increasing bias values. Figures 6(a)…”

“…Labud et.al 5 and Pal et.al 6 investigated many body interactions of different excitonic species as well as signatures of indirect excitons in quantum dot samples using standard C-V measurements in presence of light. Recently, we also reported 7 a thermodynamic model of dielectric signatures of excitonic presence in quantum well laser diodes at room temperature using capacitance measurements. Besides, long lived 8 indirect excitons are expected to play important roles in excitonic Bose-Einstein condensation 9,10 ultralow threshold, coherent, polaritonic light sources 11,12 and excitonic superconductivity 13,14 .…”

Experimental Detection and Control of Trions and Fermi-Edge Singularity in Single-Barrier GaAs/AlAs/GaAs Heterostructures Using Photocapacitance Spectroscopy

“…This definitely indicates two different physical origins for PL and photocapacitance spectra. Integrated PL intensity versus optical excitation intensity also follows a linear variation in log-log scale which gives a slope of ~ 0.96 at 100 K indicating [26] excitons as shown in Fig. 5(b).…”

“…As a result, the peak photocapacitance ratio of trions and excitons is shown to vary with the applied field, implying the formation of trions at the expense of excitons with the increase of electric field in the reverse bias regime. We tried to fit the above variation with a modified Arrhenius rate (R * ) equation [26]   …”