Shi LW, Chen YH, Xu B, Wang ZC, Wang ZG
Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Science, P.O. Box 912, Beijing 100083, People's Republic of China
Double-state lasing phenomena are easily observed in self-assembled quantum dot (QD) lasers. The effect of inter-level relaxation rate and cavity length on the double-state lasing performance of QD lasers is investigated on the basis of a rate equation model. Calculated results show that, for a certain cavity length, the ground state (GS) lasing threshold current increases almost linearly with the inter-level relaxation lifetime. However, as the relaxation rate becomes slower, the ratio of excited state (ES) lasing threshold current over the GS one decreases, showing an evident exponential behavior. A relatively feasible method to estimate the inter-level relaxation lifetime, which is difficult to measure directly, is provided. In addition, fast inter-level relaxation is favorable for the GS single-mode lasing, and leads to lower wetting layer (WL) carrier occupation probability and higher QD GS capture efficiency and external differential quantum efficiency. Besides, the double-state lasing effect strongly depends on the cavity length.
Physica E: Low-dimensional Systems and Nanostructures
Volume 39, Issue 2, September 2007, Pages 203-208