R面、C面蓝宝石上生长的InGaN多层量子点的发光性质研究

Luminescence Properties of Multi-layers InGaN Quantum Dots Grown on R and C Sapphire by a New Method

采用表面钝化和MOCVD低温生长在蓝宝石 (0 0 0 1)面 (即C面 )和蓝宝石 (110 2 )面 (即R面 )上形成了InGaN量子点 ,并构成了该量子点的多层结构。原子力显微镜测试的结果表明单层InGaN量子点平均宽约 40nm ,高约15nm ;而多层量子点上层的量子点则比单层的InGaN量子点大。R面蓝宝石衬底上生长的InGaN量子点和C面蓝宝石衬底上生长的InGaN量子点相比 ,其PL谱不仅强度高 ,而且没有多峰结构。这是由于在C面蓝宝石衬底上生长的InGaN/GaN多层量子点沿生长方向 [0 0 0 1]存在较强的内建电场 ,而在R面蓝宝石衬底上得到的多层量子点沿着生长方向 [112 0 ]没有内建电场。InGaN量子点变温光致发光 (PL)谱研究发现量子点相关的峰有快速红移现象 ,这是量子点系统所特有的PL谱特征。用在R面蓝宝石上生长的InGaN量子点作有源层有望避免内建电场的影响 ,得到高量子效率且发光波长稳定的发光器件。

Surface passivation and low temperature MOCVD were used to induce the growth of InGaN quantum dots (QDs) on (0001) sapphire (c-plane)and (l102) sapphire (R-plane),and multi-layers InGaN quantum dots structure was fabricated.The results of atomic force microscopy (AFM) tests revealed that monolayer QDs were about 40 nm wide and 15nm high while the QDs on upper layer would grow bigger.The photoluminescence intensity of multi-layers QDs grown on R sapphire was stronger than that grown on C sapphire,and there wasn't an additional peak on PL spectrum of multi-layers QDs grown on R sapphire compared with that grown on C sapphire.It could be explained that there was a strong built-in electric field along the growth orientation in the multi-layers QDs on C sapphire while no built-in electric field along the growth orientation in the multi-layers QDs grown on R sapphire. Temperature dependent PL studies revealed fast redshift of the peak energy relevant to InGaN QDs,which was the character of QDs system.Adopting InGaN QDs on R sapphire as the active layer should be a method to avoid the effect of built-in electric field and get the light emission devices with high quantum efficiency and stable emission wavelength.