ANALYSIS AND IMPROVEMENT OF GAASP/SIGE TANDEM ON SI BY IQE DATA

摘要

Potential improvements for GaAsP/SiGe tandems on Si substrates are identified by the use of IQE and related data to analyse carrier behaviour in the cells. These devices have the potential for 32% efficiency, but until now advanced device design for high performance has been made challenging by limited knowledge of material parameters, particularly for uncommon Ⅲ-Ⅴ alloy fractions. A model of optical absorption and carrier collection in the cell, including the influence of heterolayer interfaces and space charge region width, is used to fit experimental IQE data. The large number of parameters is mitigated by empirical data and limits from literature on more common alloy fractions. Measurements of IQE after etching window layers provide additional data. Carrier collection profiles and recombination parameters are found for devices with varying layer thickness, window layer materials, and material quality. The extracted parameters inform strategic changes to device structure, resulting in higher predicted currents.