Pinpi'n and pinpii'n multilayer devices with voltage controlled optical readout

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Hydrogenated amorphous silicon (a-Si:H) is a key material in thin-film electronics.
• Multispectral photodetection requires sophisticated sensor design for color resolution.
• Voltage-controlled spectral sensitivity offers a pathway to simplified multispectral sensors.

Purpose of the Study:

• To optimize a pinpii'n type a-Si:H based detector for voltage-controlled spectral sensitivity.
• To demonstrate multispectral photodetection capabilities (red, blue, green) in a single device.
• To investigate the influence of layer thickness on spectral response and threshold voltage.

Main Methods:

• Fabrication of a glass/ITO/p-i-n a-SiC:H / a-SiC:H(-p)/a-SiC:H(-i)/Si:H(-i')/SiC:H(-n)/ITO heterostructure.
• Operation in a polychromatic mode with varying electrical bias (positive and reverse).
• Numerical simulation to analyze design parameters and photon absorption.

Main Results:

• The detector achieves regionally different collection parameters, enabling multispectral photodiodes.
• Different spectral sensitivity ranges (blue, green, red) are selected by switching electrical bias.
• Threshold voltage for green/red sensitivity is dependent on the a-SiC:H (-i) layer thickness, controlling green photon confinement.

Conclusions:

• The optimized a-Si:H detector effectively resolves multiple colors (R, G, B) with a single device through voltage control.
• Layer thickness optimization, particularly of the a-Si:H i'-layer, is crucial for tuning spectral sensitivity and threshold voltages.
• This approach provides a viable method for creating simplified multispectral photodetectors.