On the unusually high photosensitivity of two barrier structures

The photoelectric characteristics of a silicon structure with oppositely directed potential barriers are studied under longitudinal illumination. The choice of the impurity density in the n + – p – n + regions ensure the joining of the depleted regions in the base. When a bias voltage is applied, the width of the regions varies at the expense of one another. During the temperature annealing (950 °C, for 20 min) of the guard band, the structure acquires short-wave (λ = 570 nm) and long-wave (λ = 850 nm) spectral photosensitivity, the numerical values of which turn out to be unusually high-up to 4 A/W and 1.2 A/W, respectively. The apparent internal amplification of the photocurrent is explained by the injection of the photogenerated carriers through the forward-biased potential barrier, which leads to a decrease in the height of both potential barriers. The internal amplification of the photocurrent up to four orders of magnitude is indicated by the ratio of the actual measured spectral photocurrent to the photocurrent calculated at the quantum yield equal to 1. The samples are characterized by low power levels equivalent to noise levels lower than 10 –12 W Hz −1/2 cm 2 .