Amorphous silicon p–i–n on p crystalline silicon photodetector in the visible and near infrared spectrum

We present a simple large area device able to discriminate between visible and near infrared (IR) radiations based on heterostructure obtained by growing p–i–n amorphous silicon junction on p-type crystalline silicon wafer. The properties of this stacked structure are those of a back to back diode. When light penetrates through the p amorphous layer and the applied voltage reverse biases the amorphous diode and forward biases the heterostructure diode visible spectrum is detected, whereas in opposite bias condition near infrared spectrum is detected. We measured these devices performing steady state and transient measurements of photocurrent in different conditions of incident light wavelength and bias voltage. An analytical model for the photocurrent is used to optimise the thickness layers. Numerical simulation with a standard simulator with integrated circuit emphasis is performed for steady state and transient measurements. Steady state measurements have shown excellent spectral separation simply by controlling external bias. Transient measurement indicates that the speed of the device in the light component detection is dependent on the speed of the p–i–n diode.