Deep levels induced by InAs/GaAs quantum dots

Photoluminescence from low temperature grown InAs∕GaAs quantum dots

“…As temperature increases, the carriers acquire enough energy to tunnel across and get trapped, thus quenching the PL efficiency with rising tem- perature. The excitation wavelength dependence confirms our observation that the PL quenching centers are located only in the GaAs barrier and not inside the QDs, which is in agreement with Deep Level Transient Spectroscopy studies reporting point defect in the nearest neighborhood [8][9][10] of the QDs within the GaAs barrier, but not within the InAs QDs themselves. In conventional high temperature grown QDs, carriers created in the barrier region above the GaAs band gap diffuse towards the QDs in which they relax down towards the QD ground state.…”

“…Another possible reason for the fine structure is the Coulomb effect between electron-hole pairs within the QD and a nearby defect state. [8][9][10] The PL peaks are superimposed on a slowly rising background extending down to 0.78 eV, which is the edge of the detector responsivity. In contradiction with the QD photoluminescence, the rising background in the spectra is not quenched at elevated temperature, as shown in Fig.…”

Deep level centers and their role in photoconductivity transients of InGaAs/GaAs quantum dot chains

“…37,38 These values of e a were found to be 0.16 6 0.02 eV, 0.18 6 0.02 eV, 0.22 6 0.02 eV, and 0.34 6 0.02 eV, which are in good agreement with the previous values observed for InGaAs/GaAs heterostructures. 17,37 Finally, if the sample is exposed to lower energy light in the "quenching" range, hv ¼ 0.83-1.0 eV, after cool down, we find that thermal stimulation results in the conductivity slowly recovering to the room temperature value throughout the temperature range. This is shown by curve 3 in Figure 8.…”

“…14,15 These deep defects are associated with an excess of As atoms or In vacancies near the InGaAs/GaAs interface for structures with InGaAs QDs or QWRs. Among the defects that form during coherent growth of the InGaAs QDs are known as the EL2 antisite (As Ga ) 16,17 and the EL6 antisite-vacancy complex (As Ga -V As ) 18 with electron capture cross-sections of r ¼ (0.8-1.7) Â 10 À13 cm 2 and r ¼ 1.3 Â 10 À13 cm 2 , respectively. The presence of these deep states around the nanostructures has an influence on (i) the mechanism of electron emission due to the local fields caused by trapped electrons and ionized defects around the QDs; (ii) fast relaxation of hot carriers in the QDs; [19][20][21] structures, taking into account the quantum confined states, the presence of deep centers, and the spatial variation of the electrostatic potential is of great importance for the further development of optoelectronic devices.…”

The fine structure of electron irradiation induced EL2-like defects in n-GaAs

“…Similarly, the 0.83 eV energy level has been observed in GaAs (as-grown) samples by other researchers and in GaAs based structures grown through molecular beam epitaxy and LEC. 17,[26][27][28] The EL2 defect can exist in two different atomic configurations, a normal configuration and a metastable one. The metastable configuration is attainable by photoquenching at low temperatures in which all the optical, magnetic, and electrical properties disappear.…”