钝化低温法生长多层InGaN量子点的结构和光学特性

采用一种新方法生长多层InGaN/GaN量子点,研究所生长样品的结构和光学特性。该方法采用了低温生长和钝化工艺,所以称之为钝化低温法。第一层InGaN量子点的尺寸平均宽度40nm,高度15nm,量子点密度为6.3×10¹⁰/cm²。随着层数的增加,量子点的尺寸也逐渐增大。在样品的PL谱测试中,观察到在In(Ga)As材料系中普遍观察到的量子点发光的温度特性---超长红移现象。它们的光学特性表明:采用钝化低温法生长的纳米结构中存在零维量子限制效应。

Structure and Luminescence Properties of Multi-sheet InGaN Quantum Dots Grown by Passivation-low-temperature Method

Multi-sheet InGaN quantum dots grown by a new method is reported, which is much different from the present quantum dots growth method. The dots are formed by de creasing the growth temperature and increasing the adatom-hopping-energy barrier through surface passivation. Thus the new method can be called as a passivation-low-temperature (PLT) method. Atomic force microscopy measurement reveal that the monolayer InGandots were small enough to expect zero-dimensional quantum effects. The size of monolayer QDs is typically 40nm wide and 15nm high. The QDs on upper layer can be grown bigger. The photoluminescence of (0001) InGaN multi-sheet QDs is measured. The PL spectra of (0001) InGaN/GaN multiple layers QDs show not only the QDs-related peak but also an additional peak. This phenomenon is attributed to the strong spontaneous and piezoelectric field along the (0001) orientation. Temperature dependent PL studies reveal the strongly zero-dimensional character of this QDs system. The experimental results show that, while for temperatur es lower than 50～60K and higher than 160K the peak energies follow the Varshni law, at the intermediate temperatures the energies decrease with increasing temperatures at a rate 6 times higher than that given by the Varshni law. The very similar phenomena were also observed in InAs QDs system. The temperature dependent PL and the AFM studies make sure that the QDs is successfully fabricated by PLT method.