Excitons for Quantum devices

Abstract

Studying the temporal behaviour of excitons in 0D-2D semiconductor structure can allow us to study the transitions between quantized energy levels. This can demonstrate quantum coherent features in time domain and establish their candidacy for quantum device applications. To probe these dynamics, we use pulsed light on the sample under study, along with applied ac and dc voltages, to create an initial state, and measure ac photo responses. Under this pulsed light excitation, the ac photo responses, i.e., photocapacitance and photoconductance show “decaying oscillatory behaviour” as a function of time. Observed oscillations of photo responses as a function of time are absent in the absence of any light pulses, i.e., under continuous light or dark. However, these oscillations are dependent on light pulse’s width, duty cycle, intensity and also on temperature and frequency of ac measurements. These rule out any experimental artefacts coming from, either movement of the light spots due to sample vibrations within CCR, or electronic circuits used to take these measurements. Moreover, we can also observe these oscillations after the light pulse. This seemingly indicates “optical free induction decay” of initial resonant state after the photo/electrical excitation is turned out of resonance. Some of these oscillations even survive for ̴100ms and present even at room temperature (300K), indicating long decoherence time and robust temperature-tolerance.