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A Resonant Tunneling Cdse Quantum Dot Photodetector For Spectral

A Resonant Tunneling Cdse Quantum Dot Photodetector For Spectral Resolution In The Visible Region

UMass Lowell Image

Joel Therrien, Electrical and Computer Engineering     

A spectrally resolving quantum dot photodetector has been designed and fabricated which is able to discriminate wavelengths in the visible region. The device consists of a monolayer of 5.4 nm diameter CdSe nanoparticles that have been sandwiched between two organic layers of Hexanedithiol, all on a highly doped p-type InP substrate. A thin, semitransparent layer of gold deposited on the top of the device made the second contact. The two layers of Hexanedithiol act as tunnel barriers for electrons inside the nanoparticles. Changing the bias voltage across the device, causes specific energy states inside the quantum dot to align with the conduction band edge of the InP. Any excited carriers in these energy levels will tunnel trough the organic barrier and be collected as photocurrent. By changing the wavelength of the incident light, the device shows a wavelength dependent I-V spectrum with jumps in the current at specific voltages. Comparing which peaks in different wavelengths are present, shows that the device has a spectrally dependent response to the incident light.