Hussain Sajid, Pozzato Alessandro, Tormen Massimo, Zannier Valentina, Biasiol Giorgio
IOM CNR, Laboratorio TASC, Area Science Park Basovizza, S.S. 14 Km 163.5, 34149 Trieste, Italy.
Department of Physics, University of Trieste, Via Valerio 2, 34128 Trieste, Italy.
Materials (Basel). 2016 Mar 18;9(3):208. doi: 10.3390/ma9030208.
Site-controlled epitaxial growth of InAs quantum dots on GaAs substrates patterned with periodic nanohole arrays relies on the deterministic nucleation of dots into the holes. In the ideal situation, each hole should be occupied exactly by one single dot, with no nucleation onto planar areas. However, the single-dot occupancy per hole is often made difficult by the fact that lithographically-defined holes are generally much larger than the dots, thus providing several nucleation sites per hole. In addition, deposition of a thin GaAs buffer before the dots tends to further widen the holes in the [110] direction. We have explored a method of native surface oxide removal by using indium beams, which effectively prevents hole elongation along [110] and greatly helps single-dot occupancy per hole. Furthermore, as compared to Ga-assisted deoxidation, In-assisted deoxidation is efficient in completely removing surface contaminants, and any excess In can be easily re-desorbed thermally, thus leaving a clean, smooth GaAs surface. Low temperature photoluminescence showed that inhomogeneous broadening is substantially reduced for QDs grown on In-deoxidized patterns, with respect to planar self-assembled dots.
在带有周期性纳米孔阵列图案的 GaAs 衬底上进行 InAs 量子点的位点控制外延生长依赖于量子点在孔中的确定性成核。在理想情况下，每个孔应恰好被一个单个量子点占据，而在平面区域上无成核现象。然而，每个孔的单量子点占据情况常常因光刻定义的孔通常比量子点大得多这一事实而变得困难，从而每个孔提供了多个成核位点。此外，在量子点沉积之前沉积一层薄的 GaAs 缓冲层往往会使孔在 [110] 方向上进一步变宽。我们探索了一种使用铟束去除原生表面氧化物的方法，该方法有效地防止了孔沿 [110] 方向伸长，并极大地有助于每个孔实现单量子点占据。此外，与 Ga 辅助脱氧相比，In 辅助脱氧在完全去除表面污染物方面效率更高，并且任何过量的 In 都可以很容易地通过热再脱附去除，从而留下干净、光滑的 GaAs 表面。低温光致发光表明，相对于平面自组装量子点，在 In 脱氧图案上生长的量子点的非均匀展宽显著降低。
