Self-assembled quantum dots based on use of dilute nitride semiconductors

首先，<1-x><l-y>利用原子氢辅助分子束外延和射频氮等离子体源在GaAs（001）衬底上制备了Ga_xIn_ N_yAs_x量子点结构。GaInNAs量子点有望将发射波长从1. 3至1.55微米及以上。我们成功地实现了1的高密度。对于<11><-2>GaAs（001）上的Ga_<0.53>In_<0.47>No_<0.02>As_<0.98>量子点，为1 × 10 ~ 4 cm ~ 2。进一步研究了H_2流量对Ga_ In_ No_As_x量子点生长动力学和光学性质的影响，发现在本系统中生长Ga_<0.53>In_<0.47>No_<0.02>As<0.98>_x量子点的最佳H_2流量为0.6sccm左右。这些结果归因于源于通过原子H的照射来改善GaInNAs量子点的晶体质量。接下来，我们研究了在GaAs（001）衬底上制备多层InAs自组装量子点的生长技术。量子点的堆叠是通过应变补偿技术实现的，其中GaNAs用作间隔层以掩埋量子点层。即使在20层堆叠之后也没有观察到位错，并且量子点的面积密度总计为10 μ cm-3的数量级<12><-2>。根据光致发光测量，在室温下在约1200 nm处清楚地观察到来自量子点的单个发射峰。此外，由于量子限制能量或势垒高度的降低，随着GaNAs间隔层中N组分的增加，发射峰值能量直接偏移到更长的波长。

First, self-assembled Ga_xIn_<1-x> N_yAs_<l-y> quantum dot structures fabricated on GaAs (001) substrates have been studied with atomic-Hydrogen assisted molecular beam epitaxy and a radio frequency nitrogen plasma source. The GaInNAs quantum dots are promising for extending emission wavelengths from 1. 3 to 1.55 um and beyond. We succeeded in achieving high densities on the order of 1. 1x10^<11> cm^<-2> for Ga_<0.53> In_<0.47> No_<0.02> As_<0.98> quantum dots on GaAs (001). Further, we studied the effect of H_2 flux on both the growth dynamics and the optical properties, and found that an optimum H_2 flux rate for Ga_<0.53> In_<0.47> No_<0.02> As_<0.98> quantum dot growth in our system is at around 0.6sccm. These results are attributed to originate from improvement of crystal quality of GaInNAs quantum dots by irradiation of atomic H.Next, we investigated a growth technique to fabricate multiple-stacked InAs self-assembled quantum dots on GaAs (001) substrates. The stacking of dots is achieved by strain compensation technique, in which GaNAs is used as a spacer layer to bury a quantum dot layer. No dislocations are observed even after 20 layers of stacking, and the area density of quantum dots amounted to the order of 10^<12> cm^<-2>. From photoluminescence measurements, a single emission peak from quantum dots is clearly observed at around 1200 nm at room temperature. Further, the emission peak energy straightforwardly shifts to longer wavelengths with increasing N composition in GaNAs spacer layer due to the lowering the quantum confinement energy or barrier height.