09:00 〜 09:15
▲ [22a-A307-1] [Young Scientist Presentation Award Speech] Al0.35GaAs / InGaP Heterojunction Solar Cell Based on Temperature-graded Growth
キーワード：MOVPE, III-V solar cell, AlGaAs
Compared with conventional InGaP solar cells, p-Al0.35GaAs/n-InGaP heterojunction cells are regarded as strong competitor since they provide better carrier collection without changing the bandgap. However, due to different preferred growth temperatures of the two materials, an inevitable temperature ramping process exists at heterojunction during metal-organic vapor phase epitaxy (MOVPE) growth, which brings about oxygen contamination and degrades open-circuit voltage (Voc).
In this study, a temperature-graded growth layer is newly introduced to achieve continuous growth at the temperature offset. More specific, between AlGaAs and InGaP grown at 700ºC and 560ºC, respectively, a thin layer of AlGaAs is slowly grown with temperature ramping down, which allows sudden switch to InGaP growth at low temperature. To validate this scheme, AlGaAs/InGaP hetero-emitter solar cells without/with grading layer, together with a InGaP reference cell, are prepared and compared via characterizations.
It is observed in J-V characteristics that the deterioration of Voc is successfully mitigated after the grading layer applied. Absolute electroluminescence and atomic force microscopy measurement are further performed to obtain external radiative efficiency (ERE) and topography at heterojunction, respectively. With improved ERE and interface evenness, it is proved that grading layer effectively suppresses oxygen incorporation at AlGaAs/InGaP heterojunction and thereby prohibits nonradiative recombination, which in turn enhances Voc. In all, the temperature-graded layer is verified to improve the quality of AlGaAs/InGaP heterojunction, which may serve as a general routine for AlGaAs-based heterogenous growth with MOVPE in the future.
In this study, a temperature-graded growth layer is newly introduced to achieve continuous growth at the temperature offset. More specific, between AlGaAs and InGaP grown at 700ºC and 560ºC, respectively, a thin layer of AlGaAs is slowly grown with temperature ramping down, which allows sudden switch to InGaP growth at low temperature. To validate this scheme, AlGaAs/InGaP hetero-emitter solar cells without/with grading layer, together with a InGaP reference cell, are prepared and compared via characterizations.
It is observed in J-V characteristics that the deterioration of Voc is successfully mitigated after the grading layer applied. Absolute electroluminescence and atomic force microscopy measurement are further performed to obtain external radiative efficiency (ERE) and topography at heterojunction, respectively. With improved ERE and interface evenness, it is proved that grading layer effectively suppresses oxygen incorporation at AlGaAs/InGaP heterojunction and thereby prohibits nonradiative recombination, which in turn enhances Voc. In all, the temperature-graded layer is verified to improve the quality of AlGaAs/InGaP heterojunction, which may serve as a general routine for AlGaAs-based heterogenous growth with MOVPE in the future.