Presentation Information
[25a-P02-4]Two-wavelength excited photoluminescence study of GaAsN/GaAs heterostructures
〇(D)Abdou Karim Niang1, Naofumi Uchiyama1, Kengo Takamiya1, Shuhei Yagi1, Hiroyuki Yaguchi1 (1.Saitama univ)
Keywords:
IBSCs and TWEPL
Dilute nitride semiconductors have exceptional physical properties, such as the large bandgap bowing [1, 2] and the conduction band splitting [3]. Among dilute nitride semiconductors, GaAsN alloys are expected to be promising materials for intermediate band solar cells (IBSCs) [4], and thus are extensively investigated. Since IBSCs utilize the absorption between intermediate and conduction bands in addition to the optical absorption between valence and conduction bands, it is important to study optical transitions between these bands. Thus, we have performed two-wavelength excited photoluminescence (TWEPL) measurements to study optical transitions in GaAsN/GaAs heterostructures.
The samples used in this study were GaAsN grown on undoped GaAs (001) substrates by metalorganic vapor phase epitaxy. The thickness of GaAsN layers was 450 nm. TWEPL measurements were carried out at 10 K using a DPSS laser (532 nm) as above gap excitation (AGE) light and a laser diode (980 nm) as below gap excitation (BGE) light. PL spectra were measured with a 300-mm monochromator and an intensified charge coupled device.
Figure 1 shows PL spectra of GaAs1-xNx (x = 0.74%) /GaAs measured by AGE only (red curve) and by the combination of AGE and BGE (blue curve). One PL peak seen at 928 nm originates from GaAsN while the other peak at 830 nm is due to GaAs. It is found from Fig. 1 that adding BGE enhances the intensity of both the PL peaks. Figure 2 shows the AGE power dependence of differential PL spectra defined as of GaAsN/GaAs. As can be seen from Fig. 2, the differential PL intensity increases with increasing AGE power. The PL intensity enhancement can be explained by the excitation of electrons from deep levels in GaAsN to the higher-lying conduction band by the BGE light followed by the relaxation to the intermediate band and the migration to GaAs.
The samples used in this study were GaAsN grown on undoped GaAs (001) substrates by metalorganic vapor phase epitaxy. The thickness of GaAsN layers was 450 nm. TWEPL measurements were carried out at 10 K using a DPSS laser (532 nm) as above gap excitation (AGE) light and a laser diode (980 nm) as below gap excitation (BGE) light. PL spectra were measured with a 300-mm monochromator and an intensified charge coupled device.
Figure 1 shows PL spectra of GaAs1-xNx (x = 0.74%) /GaAs measured by AGE only (red curve) and by the combination of AGE and BGE (blue curve). One PL peak seen at 928 nm originates from GaAsN while the other peak at 830 nm is due to GaAs. It is found from Fig. 1 that adding BGE enhances the intensity of both the PL peaks. Figure 2 shows the AGE power dependence of differential PL spectra defined as of GaAsN/GaAs. As can be seen from Fig. 2, the differential PL intensity increases with increasing AGE power. The PL intensity enhancement can be explained by the excitation of electrons from deep levels in GaAsN to the higher-lying conduction band by the BGE light followed by the relaxation to the intermediate band and the migration to GaAs.