Optical Gain of Vertically Coupled Cd0.6Zn0.4Te/ZnTe Quantum Dots

Abstract

The optical modal gain of Cd0.6Zn0.4Te/ZnTe double quantum dots was measured using a variable stripe length method, where large and small quantum dots are separated with a ZnTe layer. With a large (~18 nm) separation layer thickness of ZnTe, two gain spectra were observed, which correspond to the confined exciton levels of the large and small quantum dots, respectively. With a small (~6 nm) separation layer thickness of ZnTe, a merged single gain spectrum was observed. This can be attributed to a coupled state between large and small quantum dots. Because the density of large quantum dots (4 × 1010 cm−2) is twice the density of small quantum dots (2 × 1010 cm−2), the density of the coupled quantum dots is determined by that of small quantum dots. As a result, we found that the peak gain (123.9 ± 9.2 cm−1) with the 6 nm separation layer is comparable to that (125.2 ± 29.2 cm−1) of the small quantum dots with the 18 nm separation layer.

Electric and Magnetic Fields Effects in Vertically Coupled GaAs/AlxGa1−xAs Conical Quantum Dots

“…In Ref. [31], Mei et al measured the VCQD optical modal gain of CdZnTe/ZnTe, where the lower QD is smaller; the results showed that the peak gain of the coupled QDs, separated 6 nm, was found comparable to the large separation QDs, 18 nm. Tongbram et al [32] researched on the multi-stacked vertically coupled InAs quantum dots capped by a combinational capping layer of InAlGaAs and GaAs layer.…”