Study On Electrical And Optical Properties Of Semiconductor Multiple Quantum Well Lasers

The application of semiconductor lasers(LD)is very extensive,especially for Ga N-based LD.Its electrical and optical characteristics have been eagerly concerned by researchers.In this paper,the characteristics of the wide band gap Ga N-based multi-quantum well laser near the threshold are analyzed in detail,and some of its characteristics are compared with the narrow band gap Ga As-based semiconductor laser.The main work of this paper is as follows.(1)Using the rate equation,the different methods of defining the laser threshold current were analyzed in detail.The advantages and disadvantages of various methods were pointed out.These methods for defining the laser threshold current were analyzed in detail using the rate equation;the accuracy of the various methods was compared.It is concluded that the d~2 Sd I~2 method is more accurate to determine the threshold current,even for lasers with large spontaneous emission coefficients.The effects of spontaneous emission factor,spontaneous emission lifetime,photon lifetime and temperature on the laser threshold current obtained by various methods were also calculated.The precise functional relationship between these parameters and the threshold current was obtained.Results confirmed that the threshold region is more suitable for characterizing the laser lasing characteristics than the threshold point.(2)The rules between temperature and frequency and the electrical properties of semiconductor quantum well lasers were analyzed in detail.As the temperature increases,the threshold currents of wide-bandgap Ga N-based and narrow-bandgap Ga As-based lasers both increase;the series resistance and ideal factor of Ga N-based lasers decrease;the series resistance of Ga As-based lasers decreases but the ideal factor increases;the jump amplitude of the conductance G_p in the threshold area gradually weakened.The higher the frequency,the lower the output power of the lasers,the less obvious the negative capacitance phenomenon and the jump amplitude of the negative capacitance in the threshold area gradually decreases.The conductance G_p of Ga N-based laser gradually increases with frequency at low frequencies,but gradually decreases with frequency at high frequencies.At the intermediate frequency,G_p is not affected by frequency.The junction voltage,series resistance,and ideal factor are all affected by frequency,but there is no strict regularity.(3)The optical characteristics of the laser were analyzed in detail.The polarization characteristics of the wide bandgap and narrow bandgap lasers were explored.It was found that wide-bandgap Ga N-based lasers emit light with a very high degree of polarization at well below the threshold current.While Ga As-based lasers have a very low degree of polarization below the threshold.The spectral characteristics of the two types of lasers were measured.The results showed that the half-height width of the spectrum in the threshold region decreases rapidly,and the peak values moves weakly.Both of them no longer change above the threshold,that is,a stable lasing state is reached.Compared with the electrical characteristics,the abnormal junction voltage characteristics exhibited by the Ga N-based laser in and above the threshold region were discussed in detail.The results confirmed the difference between the junction voltage and the quasi-Fermi level separation of the Multiple Quantum Well.