Amorphous SiC/Si three-color detector

Abstract

A hydrogenated amorphous SiC/hydrogenated amorphous Si heterojunction photodetector whose peak response could be voltage adjusted to three wavelengths, i.e., 480, 530, and 575 nm, by applying a small bias within ±2 V has been successfully fabricated. The basic principle is to use two back-to-back p-i-n junction diodes (or an n-i-p-i-n transistor) in which photons with wavelength λ<500 nm (blue) are mainly collected in the front a-SiC:H/a-Si:H heterojunction and the rest (green and red) are absorbed in the rear a-Si:H homojunction. To further distinguish the green from the red, two undoped a-Si:H layers, deposited at different conditions, were used in the rear homojunction to obtain two distinct collection regions. It is found that the required voltage to select one of the collection regions is less than 2 V. This detector shows a very high rejection ratio at various responses and thus is good for distinguishing the entire color spectrum.

a-Si:H/a-SiC:H Heterostructure for Bias-Controlled Photodetectors

“…Starting from the need for a wide band-gap intrinsic layer in the front diode, the present p-i-n-i-p shows two improvements respect to n-i-p-i-n devices [4], [6] due to the fact that aSiC:H p layers can have band-gap larger than 2 eV, whereas a-SiC:H n layers show at most 1.9 eV. As a consequence: 1) front p layers enhance light transmission; 2) the front p-i junction does not suffer from band-gap mismatch; this reflects in a better electronic quality of p-i with respect to n-i interface.…”

“…In addition, the spectral profile of aSi:H absorption can be modified by adding controlled amounts of Carbon or Germanium during deposition, the resulting alloys having different band-gaps. Using this 1 .m (Ag) approach photodetectors with sensitivities 400 A (p-type a-Si) ranging from the UV to the IR can be fabricated [2], [3].Therefore, the realization 3500 A (i-type a-Si) of single devices able to detect the fundamental colors simply by varying the external bias is quite attractive [4], [5], [6]. 2000 A (n-type a-Si) In this work we describe the realization and optimization of novel p-i-n-i-p Si/SiC 700 A (i-type a-SiC) structures on Sn02/glass, acting as two-50 A (p-type a-SiC) color detectors.…”

Color-Selective CMOS Photodiodes Based on Junction Structures and Process Recipes

“…Tasi et al proposed a structure employing a change in the external bias polarity of the collector and emitter of a phototransistor. The peak wavelength varies from 600nm to 450nm under a biased voltage from -2V to 2V [4]. Since a-Si:H provides advantages of high photosensitivity in a visible light region and low-cost fabrication, it is extensively employed in the bias-controlled photosensing devices [3]- [10].…”

Stacked amorphous silicon color sensors

“…The intensity within the layer can be calculated after a few transformations, as given in (4) and (5).…”

“…Two-terminal sensors can typically be described by an anti-se- rial connection of two diodes [5]- [7], a phototransistor configuration [2], or a diode with different absorption regions for the detection of red, green, and blue light [3], [4]. Since the spectral response can be shifted from blue to green and red by the variation of the applied voltage, the color channels must be separately selected and read out sequentially.…”