Impurity free vacancy disordering of InGaAs quantum dots

Abstract

Influence of dielectric deposition parameters on the In 0.2 Ga 0.8 As / GaAs quantum well intermixing by impurity-free vacancy disordering Dependence of band gap energy shift of In 0.2 Ga 0.8 As/GaAs multiple quantum well structures by impurity-free vacancy disordering on stoichiometry of SiO x and SiN x capping layersThe effect of thermal interdiffusion on In͑Ga͒As/ GaAs quantum dot structures is very significant, due to the large strain and high concentration of indium within the dots. The traditional high temperature annealing conditions used in impurity free vacancy disordering of quantum wells cannot be used for quantum dots, as the dots can be destroyed at these temperatures. However, additional shifts due to capping layers can be achieved at low annealing temperatures. Spin-on-glass, plasma enhanced chemical vapor deposited SiO 2 , Si 3 N 4 , and electron-beam evaporated TiO 2 layers are used to both enhance and suppress the interdiffusion in single and stacked quantum dot structures. After annealing at only 750°C the different cappings enable a shift in band gap energy of 100 meV to be obtained across the sample.

Effects of rapid thermal annealing on device characteristics of InGaAs∕GaAs quantum dot infrared photodetectors

“…This has been observed previously in many studies, as a result of significant thermal interdiffusion. 9,10,13,19 However, for our 15-layer QDIP structure, the interdiffusion was initiated at a lower temperature of 700°C ͓compared with 750°C for single and 3-layer QDs ͑Ref. 10͔͒, due to a larger accumulated strain.…”

“…Hence, the technologies that have been developed in QWs cannot be transferred directly to QDs. Although interdiffusion studies have been carried out on various QD structures using the methods of rapid thermal annealing ͑RTA͒, 9,10 ion implantation, 11,12 and dielectric capping, 12,13 few device results have emerged. Midinfrared ͑3-5 m͒ and far-infrared ͑8-14 m͒ photodetectors 3,14,15 based on QDs have been predicted to have the advantages of normal incidence and high temperature operation, larger responsivity, and detectivity, in comparison to their QW counterpart.…”

InAs/GaAs quantum-dot intermixing: comparison of various dielectric encapsulants

“…This is found to promote (when GaAs surface is compressively strained) or trap (when GaAs surface is tensile strained) the V III at the interface, thus significantly affecting the intermixing process. 9,19,25,26 As the IFVD process is essentially impurity-free, the optical loss and degradation of electrical properties resulted from extended defect and free-carrier absorptions from impurity ions can be minimized to a great extent.…”

“…18 Quantum-dot intermixing (QDI) is found to be more complicated than QW intermixing due to the strong influence of the shape, size, composition, and strain distribution in and around the SAQDs. 10,19,20 Furthermore, the high sensitivity of the SAQDs to annealing parameters (temperature and duration) is very difficult to trace. So far, several SAQD intermixing techniques, such as laser radiation-induced intermixing, 21,22 neutral ion implantation-induced intermixing, 2 and impurity-free vacancy disordering (IFVD), 23,24 have been developed and studied.…”

“…For inhibiting interdiffusion, titanium oxide (TiO 2 ), 27,28 aluminum (Al), 28 and silicon nitride (Si 3 N 4 ) materials 25 were utilized. For enhancing interdiffusion, SiO 2 capping 9,24 was used.…”