Defect properties of InGaAsN layers grown as sub-monolayer digital alloys by molecular beam epitaxy

Artem Baranov (1, 2) , Alexander Gudovskikh (2, 3) , Dmitry Kudryashov (2) , Alexandra Lazarenko (2) , Ivan Morozov (2) , Alexey Mozharov (2) , Ekaterina Nikitina (2, 4) , Evgeny Pirogov (2) , Maxim Sobolev (2) , Kirill Zelentsov (2) , Anton Yu. Egorov (5) , Arouna Darga (1) , Sylvain Le Gall (1) , Jean-Paul Kleider (1)

1 GeePs - Laboratoire Génie électrique et électronique de Paris
2 SPBU - Saint Petersburg University
3 Saint Petersburg Electrotechnical University "LETI"
4 Saint-Petersburg Scientific Center
5 ITMO University [Russia]

The defect properties of InGaAsN dilute nitrides grown as sub-monolayer digital alloys (SDAs) by molecular beam epitaxy for photovoltaic application were studied by space charge capacitance spectroscopy. Alloys of i-InGaAsN (Eg = 1.03 eV) were lattice-matched grown on GaAs wafers as a superlattice of InAs/GaAsN with one monolayer of InAs (<0.5 nm) between wide GaAsN (7–12 nm) layers as active layers in single-junction solar cells. Low p-type background doping was demonstrated at room temperature in samples with InGaAsN layers 900 nm and 1200 nm thick (less 1 × 1015 cm−3). According to admittance spectroscopy and deep-level transient spectroscopy measurements, the SDA approach leads to defect-free growth up to a thickness of 900 nm. An increase in thickness to 1200 nm leads to the formation of non-radiative recombination centers with an activation energy of 0.5 eV (NT = 8.4 × 1014 cm−3) and a shallow defect level at 0.20 eV. The last one leads to the appearance of additional doping, but its concentration is low (NT = 5 × 1014 cm−3) so it does not affect the photoelectric properties. However, further increase in thickness to 1600 nm, leads to significant growth of its concentration to (3–5) × 1015 cm−3, while the concentration of deep levels becomes 1.3 × 1015 cm−3. Therefore, additional free charge carriers appearing due to ionization of the shallow level change the band diagram from p-i-n to p-n junction at room temperature. It leads to a drop of the external quantum efficiency due to the effect of pulling electric field decrease in the p-n junction and an increased number of non-radiative recombination centers that negatively impact lifetimes in InGaAsN.

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Sciences de l'ingénieur [physics]; Energie électrique

Artem Baranov, Alexander Gudovskikh, Dmitry Kudryashov, Alexandra Lazarenko, Ivan Morozov, et al.. Defect properties of InGaAsN layers grown as sub-monolayer digital alloys by molecular beam epitaxy. Journal of Applied Physics, 2018, SPECIAL TOPIC: DEFECTS IN SEMICONDUCTORS 123 (16), pp.161418 - 161418. ⟨10.1063/1.5011371⟩. ⟨hal-01739252⟩