Carrier transfer and thermal escape in CdTe/ZnTe quantum dots

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Optics

Background:

• Quantum dots (QDs) are semiconductor nanocrystals with tunable optical and electronic properties.
• CdTe/ZnTe QDs on GaAs substrates are investigated for their potential in optoelectronic devices.

Purpose of the Study:

• To investigate carrier transfer dynamics in CdTe/ZnTe quantum dots.
• To understand the mechanisms of thermal escape and nonradiative recombination in these QDs.

Main Methods:

• Time-resolved photoluminescence spectroscopy.
• High excitation intensity measurements (35 W/cm2).
• Low-temperature measurements (< 35 K).

Main Results:

• Emission energy-dependent decay time observed at high excitation intensity, attributed to lateral carrier transfer.
• A thermally activated transition between states (approx. 9 meV separation) observed at low temperature and emission energy.
• Thermal escape assisted by carrier scattering and longitudinal phonon emission (approx. 19 meV) identified as a primary nonradiative pathway at high temperatures.

Conclusions:

• Lateral carrier transfer significantly influences carrier dynamics in CdTe/ZnTe QDs.
• Phonon-assisted thermal escape is a key nonradiative process, impacting QD performance at elevated temperatures.