Study On Strong Coupling Between Photons And Excitons In InGaN/GaN Quantum Well Microcavity

InGaN/GaN quantum well(QW)has many advantages,such as high quantum efficiency,large exciton binding energy,adjustable wavelength of the luminescence,and high radiative recombination rate.These advantages make the InGaN/GaN QW be widely used in laser diodes,light-emitting diodes,exciton polariton LED,exciton polariton laser and other fields.The large exciton binding energy leads to the formation of exciton and exciton polariton at room temperature.However,in the process of InGaN epitaxial growth,fluctuations of In composition and well width are likely to occur.The resulting inhomogeneous broadening is considered to be the main reason that hinders the realization of strong exciton-photon coupling and the formation of exciton-polariton in the InGaN/GaN QW.In addition,large polarization field also has a strong impact on the property of the InGaN/GaN QW.In this paper,our research focus was on electron,exciton and exciton polariton in InGaN/GaN QW by taking into account of these effects.The main work includes:1.We propose a model to determine the polarization field and then the triangular energy band.The potential energy and wave function of the QW region were analyzed.We studied the effect of structure parameters,In composition and external bias on electron states and exciton states in single and double QWs.With the increase of well width,there is a maximum value of exciton binding energy and exciton oscillator strength,which is affected by the In composition.The polarization field will greatly reduce the exciton transition energy,leading to a decrease in the exciton transition energy.2.The absorption spectrum of InGaN/GaN QW in a microcavity at normal incidence is studied by a transfer matrix method.The characteristics of the normal mode splitting of exciton polaritons is investigated from the absorption spectrum.Method of increasing the normal mode splitting and the influence mechanism of inhomogeneous and homogeneous broadening on the splitting value are discussed.The results show that increasing the coupling exciton or photon density(such as increasing the number of QW,placing the QW at the antinode of the optical field)and decreasing the length of the cavity can enhance the normal mode splitting.There is a maximum inhomogeneous broadening value,beyond which the normal mode splitting value is vanished.The higher is the temperature and smaller is the exciton oscillator strength,the smaller is the maximum inhomogeneous broadening.At low temperature,there is an optimal inhomogeneous broadening,where the normal mode splitting value is the largest.The optimal inhomogeneous broadening has a strong dependence on temperature and exciton oscillator strength.