Theoretical and experimental study of photoelectric characteristics of the two-channel bulk charge-coupled device

Abstract

Numerical modeling and experimental studies of the photoelectric characteristics of a linear two-channel bulk charge-coupled device (CCD) with surface (<i>n</i>-type) and bulk (<i>p</i>-type) channels in the wavelength range 0.4 to 1.1 μm were accomplished. A system of two nonlinear differential equations, which describes the process of the simultaneous photorelaxation of CCD channels taking into account a diffusion component of the photocurrents from the semiconductor substrate, was determined. With the help of numerical modeling for this system, it was established that the common photorelaxation time of the channels is mainly defined by the photorelaxation process of the bulk channel, and its typical value is approximately equal to 0.5 ms (when the power density of the irradiation is 10 μW/sm²). Photoelectric measurements were carried out by means of an optical probe with a diameter of 80 rim, which was focused on the CCD surface using a stand equipped with a monochromator, a "Helios-44" lens, a filament lamp, and a condenser. The electric regime was as follows: the clock frequency of the timing negative voltage impulses was 75 kHz, and the impulse amplitude was 20 V. In theoretical and experimental investigations, different spectral photosensitivities of the channels were obtained. The maxima of their values are about 0.75 μm for the bulk channel and 0.55 μm for the surface channel. A good quantitative agreement between the theoretical simulations and the experimental investigations is shown.