Optical properties of InGaAs/InAIAs diffused double quantum wells

Abstract

The effects of interdiffusion on the subbands and optical properties of InGaAs/InAIAs double quantum well (QW) have been theoretically studied. The results show that since a double QW (DQW) can be diffused to become an effectively single QW structure, the characteristic features in the subbands structure and optical properties of a strongly coupled DQW structure and that of a single QW structure can be obtained by a suitable annealing time. Moreover, the increase in separation between the first symmetric and antisymmetric heavy hole subbands and the increase in the spin splitting of the valence subbands of the diffused DQW, due to an applied electric field, diminish when annealing time increases. In optimizing the In0.53(AlaGa1−a)0.47As/In0.52Al0.48As DQW structure, the results show that symmetric DQW with no Al content in wells can provide large material gain and radiative spontaneous recombination rate. With interdiffusion, the material gain and recombination rate reduce but the reduction saturates when the DQW structure is diffused to effectively become a single graded QW. By subjecting the DQW and an as-grown single QW to the same annealing conditions (where the summation of the width of the two wells and the separation barrier of the DQW equals the well width of the single QW), the diffused DQW can provide a larger material gain and radiative recombination rate than the diffused single QW when the annealing time is short. Therefore, the short-time diffused DQW is more useful for laser applications. Besides, since Al diffuses into the wells, the transition energy of the QW structure increases so that the operating wavelength of the optical devices can be adjusted.