Critical built-in electric field for an optimum carrier collection in multiquantum well p-i-n diodes

• Published in: Applied physics letters 1999-05, Vol.74 (19), p.2812-2814
• Main Authors: Serdiukova, I., Monier, C., Vilela, M. F., Freundlich, A.
• Format: Article
• Language: English
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.124022

The collection efficiency of carrier photogenerated in the intrinsic region of strained InAsxP1−x/InP multiquantum well p-i-n structures is analyzed. The existence of a critical threshold built-in electric field value above which total carrier collection becomes possible is demonstrated. Maximized carrier collection and high output voltage are systematically reached for built-in electric field exceeding the critical value while similar structures operating with a substantially lower built-in electric field (e.g., identical well characteristics but thicker i region) yields nonoptimized collection of carrier in this area and altered voltage output. The slight dependence of the critical electric field with the carrier confinement level is revealed, stressing out the importance of thermally activated escape energy. Finally, the results are discussed in the context of photovoltaic devices showing substantial efficiency improvement for devices designed with built-in electric fields in excess of the threshold value.