DLTS Investigations of (Ga,In)(N,As)/GaAs Quantum Wells before and after Rapid Thermal Annealing

Deep level transient spectroscopy was used to investigate deep-level defects in (Ga,In)(N,As)/GaAs triple quantum well structures grown by atmospheric pressure metalorganic vapor phase epitaxy with different indium and nitrogen contents and annealed in rapid thermal annealing system. A combination of electron traps that disappear or remain on annealing and a new hole trap that appears on annealing were detected. The revealed electron traps were attributed to N-related complexes or GaAs host-related native point defects. Moreover, it was suggested that the new hole trap observed in the annealed GaAsN/GaAs triple quantum well structure together with the dominant electron trap can act as generation-recombination center responsible for the observed a very poor optical quality among all the investigated multi-quantum well structures

Misfit Dislocations Study in MOVPE Grown Lattice-Mismatched InGaAs/GaAs Heterostructures by Means of DLTS Technique

Two deep traps associated with lattice-mismatch induced defects in n-type In$\text{}_{0.042}$Ga$\text{}_{0.958}$As/GaAs heterostructures and three deep point traps were observed by means of DLTS method. In order to determine the overlapping DLTS-line peaks parameters precisely, high resolution Laplace DLTS studies werw performed. A simple procedure of distinguishing between point and extended defects in DLTS measurements was used

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

International audienceThe 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