Nanocomposites and nanomaterials

New Defect Levels in InAs/In0.15Ga0.85As Quantum Dot Structure Detected by Thermally Stimulated Current Spectroscopy
Datsenko O.I.1, Golovynskyi S.2,3, Seravalli L.4, Trevisi G.4, Frigeri P.4, Babichuk I.S.2,3, Golovynska I.2, Qu Junle2
1 Department of Physics, Taras Shevchenko National University of Kyiv, Kyiv 01601, Ukraine.
E-mail: lesoto8g@gmail.com
2 Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, People’s Republic of China
3 Institute of Semiconductor Physics, NAS of Ukraine, Kyiv 03028, Ukraine.
4 Institute of Materials for Electronics and Magnetism, CNR-IMEM, I-43124 Parma, Italy.

An in-depth study of an InAs/In0.15Ga0.85As quantum dot structure is carried out by thermally stimulated current spectroscopy. In addition to point defects EL2, EL6, EL7, EL9, EL10 and three extended defects ED1-ED3 found earlier [1], new bands are detected in the spectra by varying excitation and delay time. 
Thus, the band of ED3 trap at 210 K (0.42-0.43 eV below the conduction band) is found to be compound confirming the assumption [1] about an overlap with the signal from the point defect EL5 [2]. The band near 150 K (~ 0.29-0.30 eV) of EL7 defect has been separated into two ones corresponding to activation energies of 0.29 and 0.30 eV, revealing moreover a contribution near 135 K (0.27 eV), which could be an evidence of the EL8 defect reported by Martin et al. at 0.27 eV [2].
Furthermore, a new band at 97 K (0.19 eV) is found between the characteristic bands of EL10 (0.17 eV) and EL9 (~0.23 eV), showing that the list of the shallow defects reported in In(Ga)As/(In)GaAs nanostructures should be extended.

1.	Golovynskyi S., Datsenko O., Seravalli L., Kozak O., Trevisi G., Frigeri P., Babichuk I. S., Golovynska I. and Qu J. Deep levels in metamorphic InAs/InGaAs quantum dot structures with different composition of the embedding layers // Semicond Sci Technol.-2017.-32, N 12.-P. 125001.
2.	Martin G. M., Mitonneau A. and Mircea A. Electron traps in bulk and epitaxial GaAs crystals // Electron Lett.-1977.-13, N 7.-P 191-193.