We investigated the effects of ZnTe separation layer thickness on the optical properties of asymmetric CdTe/ZnTe double quantum dots (QDs) deposited by molecular beam epitaxy and atomic layer epitaxy on Si substrates. For asymmetric CdTe/ZnTe double QDs, the exitonic peaks of the large QDs (LQDs) were blue shifted with decreasing separation layer thickness because of intermixing caused by strain from the small QDs (SQDs). The relative peak intensity of the LQDs with respect to that of the SQDs increased with decreasing separation layer thickness due to carrier tunneling from the SQDs to the LQDs. We propose that the separation layer plays a key role in the thermal escape process, and can therefore be used to modulate carrier capture in optoelectronic devices.