InGaAs/GaAs应变量子阱的光谱研究

Spectral Study of InGaAs/GaAs Strained Quantum Wells

分别用光致发光谱(PL)、光伏谱(PV)及时间分辨谱(TRPL)的方法,测量了应变InGaAs/GaAs单量子阱和多量子阱在不同温度下的光谱,发现单量子阱与多量子阱有不同的光学性质。多量子阱PL谱发光峰和PV谱激子峰的强度与半高宽都比单量子阱的大,但单量子阱的半高宽随着温度的升高增大很快,这是由激子 声子耦合引起的。通过时间分辨谱研究发现了量子阱子能级之间的跃迁,多量子阱的发光寿命明显比单量子阱的长。我们利用形变势模型对量子阱的能带进行了计算,很好地解释了实验结果。

Methods of photoluminescence(PL) photovoltage(PV), and timeresolved spectrum(TRS) are applied to study InGaAs/GaAs strained quantum well. We discover singlequantum well(SQW) and multiquantum well(MQW) have different spectral properties; and spectral intensity of MQW is much higher and spectral full width at half maximum (FWHM) is larger than those of SQW, but spectral FWHM of SQW increases more quickly than that of MQW, which is caused by excitonLO phonon coupling. The peaking energy of 11H obtained from PV spectrum has a little redshift compared with that from PL spectrum, which is called Stokes shift. TRS at different temperature shows luminescence delay of all three samples accords with one order at low temperature. But when the temperature is up to 70K,luminescence delay of Sample A accords with two orders, while luminescence delay of Sample B and Sample C still accord with one order. Luminescence delay with one order means one process of luminescence delay and luminescence delay with two orders means two processes of luminescence delay. Considering the different width of the three samples, we know that there are more than one sublevels in conduction or valence band of Sample A. But for the narrower width of quantum well, Sample B and Sample C have only one sublevel in conduction or valence band. As the temperature rises to 70K, KT approximates the transition energy from the first sublevel to the second one in valence, which suggests that transition may occur among valence interbands of Sample A and this transition causes luminescence delay of Sample A according with two orders when the temperature is up to 70K. We also observe that PL lifetime of MQW is longer than that of SQW,which is due to quantum tunneling effect in MQW at low temperature. The transition peaks of PV spectra and PL spectra have been identified compared with the theoretical calculation by KronigPenney model.