Light Wavelength Effects on Performance of a-Si:H PIN Photodiodes
- PDF / 326,989 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 110 Downloads / 201 Views
Light Wavelength Effects on Performance of a-Si:H PIN Photodiodes Shu-Hsien Wu, Yue Kuo, and Chi-Chou Lin Thin Film Nano &Microelectronics Research Laboratory, Texas A&M University, College Station, TX, 77843-3122 ABSTRACT Light effects on the performance of the a-Si:H PIN photodiode has been studied. The leakage current-voltage and capacitance-voltage curves under the red, green and blue light illuminations were measured. The apparent charge storage density in the negative voltage range was quantified from the capacitance-voltage curve; charges in the positive voltage range were estimated from the leakage current-voltage curve. A comparison of charge storage capacities of diodes with different intrinsic layer thicknesses is also presented. The diode under the long wavelength light illumination condition stored more charges than that under the short wavelength light illumination condition because the former could penetrate the intrinsic a-Si:H layer deeper than the latter could. The leakage current and charge storage capacity of the diode are determined by the generation of electron-hole pairs, the depletion of charges in the intrinsic layer, and the supply of charges from the electrodes. The number of incident photons is critical to the process. INTRODUCTION The amorphous silicon (a-Si:H) PIN diode poses a number of unique properties such as broad spectral response, large area capability, high radiation resistance, low fabrication cost and easy to integrate with read-out devices, which are suitable for many electronic and optoelectronic applications [1,2,3]. This kind of device provides a new impetus for image sensing, such as document scanners, X-ray and charged particle detectors, and high-quality imagers. There are many detailed researches on how to improve its performance and efficiency since 1980s [4]. Antonuk, et al. [5,6,7] reported the result on the charge storage of the a-Si:H PIN diode in the active matrix flat-panel imager (AMFPI) for the x-ray imaging application. Charges stored in the diode were read out by the amplifier, which was then transformed into the image signal. In this study, the charge storage capacity of a single a-Si:H PIN diode under different light illumination conditions is studied. EXPERIMENTAL The a-Si:H PIN stack was deposited by a plasma enhanced chemical vapor deposition (PECVD) system, which has the parallel-plate electrodes driven by a 13.56 MHz RF generator. The film was deposited on the corning 1737 glass substrate pre-coated with a sputter deposited Mo (150 nm) film. The films thicknesses are: n+ (300 Å), intrinsic (i-layer) (0.3 or 2 μm), and p+ (300 Å). The n+ film was deposited at a rate of 4 nm/min from SiH4/PH3 (6.88% in H2)/H2 10 sccm/10 sccm/ 1,000 sccm, at 500 W, 750 mT, and 250 °C. The i-layer film was deposited at a rate of 6 nm/min from SiH4 50 sccm at 80 W and 150 mT. The p+ film was deposited at a rate of 10 nm/min from SiH4/B2H6 (2% in H2)/H2 10 sccm/20 sccm/1,000 sccm, 500 W, and 750 mT. The PIN tri-layer stack was deposited in one pumpdown in the same chamber w
Data Loading...
